A few key definitions excerpted from the Oxford English Dictionary:
"...A licence conferring the sole right to manufacture, sell, or deal in a product or commodity; (now) spec. a licence from a government conferring for a set period the sole right to make, use, or sell some process or invention; a right conferred in this way."
"...A general name for property (such as patents, trademarks, and copyright material) which is the product of invention or creativity, and which does not exist in a tangible, physical form."
"...To give (a person) permission to (do something)."
"...A mark (secured by legal registration or, in some countries, established by use) used by a manufacturer or trader to distinguish his goods from similar wares of other firms; usually a distinctive device or figure, a fancy name or trade name, or the name of an individual or firm, marked or impressed on the article or upon the package, etc., in or with which it is sold."
These tools allow you to do quick, keyword, searches for patents. You can also search by inventor and assignee (the person or company that holds the rights to that patent).
Patent classification is a way the that patent examiners arrange documents according to the patent's technical features. Classification searching allows searchers to quickly find a document disclosing the invention identical or similar to the invention for which a patent is claimed. Patents may have more than one classification.
These databases that you may already be using also include patents:
Below are a few resources recommended by the above article when conducting a trademark search: