A trademark ("mark") is a word or words, or symbol or graphic design, or combinations of these elements that designate the source of products (goods) – it’s a brand name or logo.
Trademarks are displayed on the products and/or the packaging. A service mark is a mark used for services.
Trademark rights provide protection against unauthorized use of a confusingly similar mark.
Trademark rights are created by commercial use of the trademark. The ™ trademark symbol, or the SM service mark symbol, should be displayed after unregistered marks. Word marks should also be distinguished from neighboring text by a different font style and/or font size.
Federal registration enhances the protections given to the trademark rights created by proper use. The ® registration symbol should be displayed after federally registered marks
The ® registration symbol should never be displayed after marks that are not federally registered.
A generic term for the product or service sold is not eligible for registration or protection.
Words that describe the product or service, or a feature thereof, or an ingredient therein, are not eligible for registration on the Principal Register until secondary meaning has attached to mark (words recognized by consumers as a brand name, rather than a descriptor).
For a complete list of terms necessary to understand trademarks, visit the USPTO - Glossary page.
There are several USTPO-produced videos to help you understand the trademark searching and filing process.