In short, a patent is a grant of specific property rights for an invention in exchange for full public disclosure of the details of the invention. Patents are typically issued by a government body. In the United states, that body is the United States Patent and Trademark Office (USPTO).
According to the USPTO...
The right conferred by the patent grant is, in the language of the statute and of the grant itself, “the right to exclude others from making, using, offering for sale, or selling” the invention in the United States or “importing” the invention into the United States. What is granted is not the right to make, use, offer for sale, sell or import, but the right to exclude others from making, using, offering for sale, selling or importing the invention. Once a patent is issued, the patentee must enforce the patent without aid of the USPTO.
Much patent information is never disclosed or published elsewhere. Patents contain a wealth of specific technical detail, research data, and drawings. Patents and patent applications often contain information on new advances long before that information is published in a journal article.
You can use several websites to search US and world patents by keyword. However, be warned that this will likely give you incomplete results. Sources for keyword searching of patents are listed below.
Because patents are written using obfuscating and otherwise difficult language, one of the best ways to ensure a complete search is to use the Cooperative Patent Classification assigned to patents for particular types of technologies. By using the classification codes, you can find all patents for similar objects or technologies without having to guess the words used by the authors of the patents.