The rolling pin or rolling-pin is a kitchen tool used mainly in baking, where it's commonly called on to flatten blobs of dough for things like pie crust, biscuits, and cookies. It's also used to crush crackers and dry bread to make crumbs and flattening chicken breasts.
Most commonly rolling pins are made from hardwood, but they are also formed from marble, plastic, glass, ceramic, porcelain, and even brass or copper. Ideally your rolling pin should be heavy, because heavier pins produce smoother doughs with less expended effort. The easiest to use pins are the American ones; they have handles anchored with a steel rod that runs through the cente of the pin and is fitted with ball bearings; these allow the shaft of the pin to turn while the handles stay still.
Many professionals prefer the European pole pin; these can be either straight or tapered at the ends. The tapered ones are preferable because they allow greater manoueverability, but take some getting used to. If you aspire to culinary greatness, though, you should know that chefs prefer pole pins because they allow them to get a good "feel" for the dough under their palms, and if you're going to be great you're going to have to develop such second senses about food too.
Ceramic, glass, marble, and plastic pins are cooler in temperature than wooden pins; some are even hollow and can be filled with ice, handy if you're working with delicate dough that becomes difficult when warm. Which you will do at some point, if you aspire to lofty culinary heights.