A concert tour is a series of concerts by an artist or group of artists in different cities or locations. Often, concert tours are named, to differentiate different tours by the same artist and associate a specific tour with a particular album or product (for example: Michael Jackson's Bad Tour). Especially in the popular music world, such tours can become large-scale enterprises that last for several months or even years. They are seen by thousands or millions of people, and bring in millions of dollars (or the equivalent) in ticket revenues. 