The legal right granted to an author, composer, playwright, publisher, or distributor (Or Software Author) to exclusive publication, production, sale, or distribution of a literary, musical, dramatic, or artistic (or programmatic) work.

Compare CopyLeft.

Everything you create is automatically assigned copyright (which lasts a limited term: or if you're in America, for the rest of the Universe's natural existance, it would seem). You can remove copyright from something and put it in the PublicDomain.

Note: (c) is NOT legally enforcable as a copyright symbol. Don't use it. Ever. You need a C in a closed circle, like such: ©

But this doesn't matter so much now that the countries that are signatories to the Berne Convention on copyright automatically assign copyright on created works. Before that, you did need to explicitly declare your copyright...?

The way that copyright laws were originally written, you were not breaking any law by merely possessing copyrighted items without the copyright holder's permission, unless and until you re-distributed (or publicly displayed etc) the item (or a copy of the item). It appears that recent law changes in America have changed this status quo (for Americans, at least).

See also: IntellectualProperty, Patent, SoftwarePatent