A trademark is a word or symbol used in commerce to indicate the source of products or goods, that is, to distinguish one's goods from those of another.  The key is that, for ownership rights to attach, the mark must be actually (or specifically intended to be) used commercially where it can be identified by the consuming public.  Similarly, a service mark may identify the services of an individual or company. Unlike a patent, which need not be used commercially to continue in force, a tradement must be used. And, if it is not used, or if the owner does not vigorously keep others from using the trademark, the rights may be lost. (Examples include thermos, dry ice and escalator.)  Trademarks may be protected through common law (simply by using the mark in commerce) or through state or federal registration.