Although both protect ideas, there are several differences between a copyright and a patent. A copyright protects work of authorship that is fixed in a tangible medium of expression such as books, plays, or songs. Patents protect the useful aspects of a particular invention. What's the difference? Well, if I write a copyright law, it starts with books. The entire law of copyright came from books. It came with the printing press to stop others from physically reproducing those exact words on a piece of paper. So any work of authorship is protected by copyright. That concept of books has been expanded to photographs and music, stopping someone else from copying the music from one place to another, or copying the song, or copying the playwright script and the actual performance of a play potentially that is fixed in a DVD or CD onto another DVD or CD. Copyright protects copying, the physical manifestation of the work of authorship that is fixed in that tangible medium, from one place to the other. Patents protect useful ideas that are inventions, that are protected through this grant of a limited monopoly right. The term of copyright is much longer than that of patents. Patents only last 20 years from the date of filing. Copyrights typically last 75 to 120 years mostly.
It is also much harder to get a patent than it is to get a copyright. Copyright protection is automatic. Once that work of authorship is fixed in a tangible medium of expression, whether or not you put the © or not – it is always good to put © at the bottom – Copyright 2007, 2008. If you do not put that, you still have a copyright interest in that work. It is different with patents. With patents, you have to go through a scrutiny process to see is your invention really new or not. So patents and copyrights cover different things. There are two areas where there is an overlap between patents and copyrights. Those two areas are one, physical ornamental features of articles, like a design of a new kind of mouse or laptop computer. That can be protected, the ornamental features, through a design patent, a particular kind of patent that protects ornamental features. It might also be protected under copyright if it is sufficiently artistic enough to qualify to be a work of authorship.
The other area where there is some overlap between copyrights and patents is software. In software, the actual source code of the software, to prevent someone from copying that source code from one hard drive to another or stealing the code and putting in another program, is protected through copyright, but the useful aspect of what that source code does, the program and how it functions and if it is new and it is an invention can be protected through patents.