Any recognizable sign, expression, design, logo or slogan which identifies a product or a service can be trademarked by registration through the government trademarks office. Once a trademark is registered and issued, the use of that trademark belongs to the owner for exclusive use, and while it can be licensed for use by other commercial entities, it cannot be used without a license and/or a royalty.
Trademarks of popular products such as Coca Cola are carefully protected. Should the brand name fall into the common lexicon – such as “Have a Coke” to represent any cola drink – this can break a trademark and leave it in the public domain. This occurred with Kleenex and Jeep to an extent, although both companies worked diligently to stop others from using their brand names out of context.
Once a company or individual has achieved success, their trademark can be licensed to others so that the quality and reputation of the original will be associated with and transferred to the licensee, bringing value at a cost. An example is the Trump name, which generates more revenue as a symbol than if the owner owned the properties himself.