This is the best summary of the differences I've seen
http://www.caromcues.com/CaromvsPoolCues.htm
Carom versus Pool Cues: In general, pool and carom players use distinctly different cues from one another. While certain individuals are skilled at both games using only one cue, they are the exception. Pool players predominantly use a 58-inch, 19 oz average weight cue with a 12.75 to 13.25 mm tip. The joint of a pool cue normally incorporates a steel bolt and may have a steel collar as well. Shaft flex varies widely among pool players, with entire segments of the population insisting that their particular taper and flex is THE ultimate and final solution to the hotly debated issue of "squirt," deflection, power, etc. The challenges and counter-challenges among pool cue makers over such matters is the marketing manager's dream (or nightmare, as the case may be.)
Carom players, on the other hand, whose distribution worldwide is probably greater than pool, have long since settled the issue to their general satisfaction. Carom cues are shorter, typically from 54 to 56 inches long, lighter, typically 16.5 to 18.5 ounces, and use 11-12 mm tips, only rarely smaller or larger. Carom cues traditionally have joints that include wooden threads on the end of the shaft, or some other joint that minimizes the weight in the joint because carom players prefer their cues to balance more under the hand. A carom cue has a thicker butt and commonly a much thicker joint than a pool cue, and the overall taper of the cue shaft, with a few notable exceptions, is nearly conical from joint to tip. Summarily, a carom cue is much stiffer than a pool cue. A carom ball weighs almost exactly an ounce more than a pool ball (some varieties even more); hence more energy is required to drive it around a table. A carom player wishes to develop such touch for the game that they can repeatedly control the distance a ball covers, perhaps after traveling 3 times around the table, to a final destination within 2 inches of a given spot on the table. A stiff cue permits developing that touch better than a flexible cue. Additionally, carom billiards uses much more controlled extreme english than pool. Being able to repeat the effect of a given english is vital to a carom player; a stiff shaft, which flexes less and absorbs less energy in the hit, permits that repeatability. Among carom players, the choice of cue length, weight, and tip is driven by the specific game, from the very light cue normally used in the "small" games, straight-rail and balkline, to the slightly heavier cues used for 3-cushion. The emphasis on stiffness is generally constant.
Hernan7 said:
Hey what's up guys !!! This time I have a new question. Well, I've been playing caroms with a pool cue, but to be honest I do not know the difference between a pool cue and a carom cue other than the size of the tip but I really don't know how that affects my playing. Here is the link to a previous thread that I posted showing some pictures of my cue, all I know is that my cue is a Myron cue. Could you guys tell me if it's necessary to make some changes to my cue in order to improve my game, and if so, what changes should my cue suffer in order to become a carom cue? Thank you very much for your time guys, I'll be waiting for your responses.
) than just buying a regular carom cue. Your chances of rather getting a regular job and waisting around $400 for a carom cue is just better than selling your guitarra. 
. Enjoy!