To contribute something is to provide a part of the whole. When your company has their annual softball game and potluck picnic, you will probably be asked to contribute a dish, like your famous macaroni salad.
Contribute comes from a Latin word that means “to bring together, add, or unite.” When you contribute to a cause, you are adding to what other people have kicked in, which makes the effort complete. You can contribute your singing talent to a traveling a cappella group; you can contribute money or time to save rhinoceroses; you can contribute cupcakes to the gymnastics team bake sale; or you can even contribute ideas on healthcare reform to a Washington think tank.