A tagline, or often called a strapline in the UK, is a slogan that is designed to work with the product or company's brand. Instead of a slogan that contains the name of the brand, the tagline is a modifier that usually follows immediately after the brand or company name. The advantage of using a tagline is that it is closely associated with the brand.
Research has shown that some of the best slogans are remembered by everyone, but not necessarily associated with the brand they promote. Using a tagline delivers a brief message about the company or product that can be changed from time to time if the product changes or the company moves in a new direction.
Some examples of taglines:
Xerox. The document company.
7-UP - the uncola.
Nike. Just do it.
Avis. We try harder.
DeBeers. A diamond is forever.
GE. We bring good things to life.
BMW. The ultimate driving machine.
Taco Bell. Think outside the bun.