A rolling pin is a rigid cylinder which is used for rolling out all kinds of dough.
If you intend to buy:
Choose a simple, solid rolling pin (rather than with attached handles); the ideal is a wooden roller 45 cm long and 5 cm in diameter (18 inches long and 2 inches in diameter). If you have a handy friend or relative who can make one like this for you, so much the better. Mine, for example, that you can see the photos, was made by my father from a piece of beech and is perfect.