This document summarizes key aspects of trademark law and registration. It defines trademarks as identifying the source of goods and distinguishes them from trade names, copyrights and patents. The advantages of registering a trademark are described as providing public notice, legal presumption of ownership nationwide and exclusivity. Infringement depends on the similarity of marks and relatedness of goods/services. The strength of a mark determines how much protection it receives, with fanciful/arbitrary marks receiving the most.