A trademark is a brand name. A trademark or service mark includes any word, name, symbol, device, or any combination, used or intended to be used to identify and distinguish the goods/services of one seller or provider from those of others, and to indicate the source of the goods/services.
Although federal registration of a mark is not mandatory, it has several advantages, including notice to the public of the registrant's claim of ownership of the mark, legal presumption of ownership nationwide, and exclusive right to use the mark on or in connection with the goods/services listed in the registration.
For additional information, consult Protecting Your Trademark: Enhancing Your Rights through Federal Registration published by the United States Patent and Trademark Office.
Strong marks - These marks are easier to protect than others and will be the easiest for you to present third-party usage of the mark. Strong marks can be registered with the US Patent and Trademark Office and are therefore easier to legally protect.
Weak marks - These marks are probably being used by others to describe a good or service and are difficult and costly to police and protect. Weak marks are not registrable and are difficult to protect.