Patents use very unusual language, so you may need to think of very different terms to find a patent. For example, a patent for a cell phone case may be called a protective enclosure for an electronic device.
For someone unfamiliar with patent classifications, Google Patents will be your best resource for searching.
NOTE: Trademarks and copyrights are different from patents!
For more information about patents:
Inventions must meet specific criteria. An invention must be: