Corks are small, cylindrical pieces typically made from the bark of the cork oak tree. They are primarily used to seal bottles, especially for wine, to keep the contents fresh and prevent oxidation. The natural properties of cork make it an ideal material, as it is lightweight, buoyant, and impermeable to liquids and gases. In addition to wine bottles, corks are also used in various other applications, such as sealing bottles of champagne and olive oil. They can be found in craft projects and as bulletin board materials due to their sound-absorbing qualities.