A baster is a large tube made of metal, plastic or glass, with a small opening on one end and a rubber bulb at the other end. The baster can be filled with drippings, broth, butter and other sauces for basting purposes while food is cooking.
According to HowStuffWorks, a baster can also have a small brush at the end. The act of basting helps to preserve the moisture in meats and provide flavor. Seasonings can be added to the liquid used for basting. The bulb baster provides a way for a cook to extract liquid from a pan to then squeeze onto the food that is cooking.