The following Description of the Collie can be found on the American Kennel Club website:

Additional Information can be found at The Collie Club of America.

I do recommend reading the literature on the Collie Club website to determine if the Collie is the breed for you.  It is a .pdf file so you will need Adobe Acrobat.

Rough

General Character
The Collie is a lithe, strong, responsive, active dog, carrying no useless timber, standing naturally straight and firm. The deep, moderately wide chest shows strength, the sloping shoulders and well-bent hocks indicate speed and grace, and the face shows high intelligence. The Collie presents an impressive, proud picture of true balance, each part being in harmonious proportion to every other part and to the whole. Except for the technical description that is essential to this Standard and without which no Standard for the guidance of breeders and judges is adequate, it could be stated simply that no part of the Collie ever seems to be out of proportion to any other part. Timidity, frailness, sullenness, viciousness, lack of animation, cumbersome appearance and lack of over-all balance impair the general character.

Head
The head properties are of great importance. When considered in proportion to the size of the dog the head is inclined to lightness and never appears massive. A heavy-headed dog lacks the necessary bright, alert, full-of-sense look that contributes so greatly to expression. Both in front and profile view the head bears a general resemblance to a well-blunted lean wedge, being smooth and clean in outline and nicely balanced in proportion. On the sides it tapers gradually and smoothly from the ears to the end of the black nose, without being flared out in backskull (cheeky) or pinched in muzzle (snipy). In profile view the top of the backskull and the top of the muzzle lie in two approximately parallel, straight planes of equal length, divided by a very slight but perceptible stop or break. A mid-point between the inside corners of the eyes (which is the center of a correctly placed stop) is the center of balance in length of head.

The end of the smooth, well-rounded muzzle is blunt but not square. The underjaw is strong, clean-cut and the depth of skull from the brow to the under part of the jaw is not excessive. The teeth are of good size, meeting in a scissors bite. Overshot or undershot jaws are undesirable, the latter being more severely penalized. There is a very slight prominence of the eyebrows. The backskull is flat, without receding either laterally or backward and the occipital bone is not highly peaked. The proper width of backskull necessarily depends upon the combined length of skull and muzzle and the width of the backskull is less than its length. Thus the correct width varies with the individual and is dependent upon the extent to which it is supported by length of muzzle. Because of the importance of the head characteristics, prominent head faults are very severely penalized.

Eyes
Because of the combination of the flat skull, the arched eyebrows, the slight stop and the rounded muzzle, the foreface must be chiseled to form a receptacle for the eyes and they are necessarily placed obliquely to give them the required forward outlook. Except for the blue merles, they are required to be matched in color. They are almond-shaped, of medium size and never properly appear to be large or prominent. The color is dark and the eye does not show a yellow ring or a sufficiently prominent haw to affect the dog's expression. The eyes have a clear, bright appearance, expressing intelligent inquisitiveness, particularly when the ears are drawn up and the dog is on the alert. In blue merles, dark brown eyes are preferable, but either or both eyes may be merle or china in color without specific penalty. A large, round, full eye seriously detracts from the desired sweet expression. Eye faults are heavily penalized.

Ears
The ears are in proportion to the size of the head and, if they are carried properly and unquestionably break naturally, are seldom too small. Large ears usually cannot be lifted correctly off the head, and even if lifted, they will be out of proportion to the size of the head. When in repose the ears are folded lengthwise and thrown back into the frill. On the alert they are drawn well up on the backskull and are carried about three-quarters erect, with about one-fourth of the ear tipping or breaking forward. A dog with prick ears or low ears cannot show true expression and is penalized accordingly.

Neck
The neck is firm, clean, muscular, sinewy and heavily frilled. It is fairly long, carried upright with a slight arch at the nape and imparts a proud, upstanding appearance showing off the frill.

Body
The body is firm, hard and muscular, a trifle long in proportion to the height. The ribs are well-rounded behind the well-sloped shoulders and the chest is deep, extending to the elbows. The back is strong and level, supported by powerful hips and thighs and the croup is sloped to give a well-rounded finish. The loin is powerful and slightly arched. Noticeably fat dogs, or dogs in poor flesh, or with skin disease, or with no undercoat are out of condition and are moderately penalized accordingly.

Legs
The forelegs are straight and muscular, with a fair amount of bone considering the size of the dog. A cumbersome appearance is undesirable. Both narrow and wide placement are penalized. The forearm is moderately fleshy and the pasterns are flexible but without weakness. The hind legs are less fleshy, muscular at the thighs, very sinewy and the hocks and stifles are well bent. A cowhocked dog or a dog with straight stifles is penalized. The comparatively small feet are approximately oval in shape. The soles are well padded and tough, and the toes are well arched and close together. When the Collie is not in motion the legs and feet are judged by allowing the dog to come to a natural stop in a standing position so that both the forelegs and the hind legs are placed well apart, with the feet extending straight forward. Excessive "posing"is undesirable.

Gait
Gait is sound. When the dog is moved at a slow trot toward an observer its straight front legs track comparatively close together at the ground. The front legs are not out at the elbows, do not "crossover," nor does the dog move with a choppy, pacing or rolling gait. When viewed from the rear the hind legs are straight, tracking comparatively close together at the ground. At a moderate trot the hind legs are powerful and propelling. Viewed from the side the reasonably long, "reaching" stride is smooth and even, keeping the back line firm and level.

As the speed of the gait is increased the Collie single tracks, bringing the front legs inward in a straight line from the shoulder toward the center line of the body and the hind legs inward in a straight line from the hip toward the center line of the body. The gait suggests effortless speed combined with the dog's herding heritage, requiring it to be capable of changing its direction of travel almost instantaneously.

Tail
The tail is moderately long, the bone reaching to the hock joint or below. It is carried low when the dog is quiet, the end having an upward twist or swirl. When gaited or when the dog is excited it is carried gaily but not over the back.

Coat
The well-fitting, proper-textured coat is the crowning glory of the rough variety of Collie. It is abundant except on the head and legs. The outer coat is straight and harsh to the touch. A soft, open outer coat or a curly outer coat, regardless of quantity is penalized. The undercoat, however, is soft, furry and so close together that it is difficult to see the skin when the hair is parted. The coat is very abundant on the mane and frill. The face or mask is smooth. The forelegs are smooth and well feathered to the back of the pasterns. The hind legs are smooth below the hock joints. Any feathering below the hocks is removed for the show ring. The hair on the tail is very profuse and on the hips it is long and bushy. The texture, quantity and the extent to which the coat "fits the dog" are important points.

Color
The four recognized colors are "Sable and White," "Tri-color," "Blue Merle" and "White." There is no preference among them. The "Sable and White" is predominantly sable (a fawn sable color of varying shades from light gold to dark mahogany) with white markings usually on the chest, neck, legs, feet and the tip of the tail. A blaze may appear on the foreface or backskull or both. The "Tri-color" is predominantly black, carrying white markings as in a "Sable and White" and has tan shadings on and about the head and legs. The "Blue Merle" is a mottled or "marbled" color predominantly blue-grey and black with white markings as in the "Sable and White" and usually has tan shadings as in the "Tri-color." The "White" is predominantly white, preferably with sable, tri-color or blue merle markings.

Size
Dogs are from 24 to 26 inches at the shoulder and weigh from 60 to 75 pounds. Bitches are from 22 to 24 inches at the shoulder, weighing from 50 to 65 pounds. An undersize or an oversize Collie is penalized according to the extent to which the dog appears to be undersize or oversize.

Expression
Expression is one of the most important points in considering the relative value of Collies. Expression, like the term character is difficult to define in words. It is not a fixed point as in color, weight or height and it is something the uninitiated can properly understand only by optical illustration. In general, however, it may be said to be the combined product of the shape and balance of the skull and muzzle, the placement, size, shape and color of the eye and the position, size and carriage of the ears. An expression that shows sullenness or which is suggestive of any other breed is entirely foreign. The Collie cannot be judged properly until its expression has been carefully evaluated.

Smooth

The Smooth Variety of Collie is judged by the same Standard as the Rough Variety, except that the references to the quantity and distribution of the coat are not applicable to the Smooth Variety, which has a short, hard, dense, flat coat of good texture, with an abundance of undercoat.