A trademark is a type of intellectual property that distinguishes the source of goods and services through names, words, designs or other identifiers. Trademarks can be registered under classes such as chemicals, machines or medical instruments. There were several famous trademark disputes including between Apple Corps and Apple Computer over the Apple name, which was finally settled in 2007 when Apple bought the trademark rights. Another case was between the environmental group WWF and the World Wrestling Federation over the initials WWF, which resulted in the wrestling group changing its name to WWE.