A call girl or female escort is a prostitute who (unlike a street walker) does not display her profession to the general public, nor does she usually work in an institution like a brothel, although she may be employed by an escort agency. The client must make an appointment, usually by calling a telephone number. Call girls often advertise their services in small ads in magazines and via the Internet, although an intermediary advertiser, such as an escort agency, may be involved in promoting escorts, while, less often, some may be handled by a pimp. Call girls may work either incall, where the client comes to them, or outcall, where they go to the client. Some porn stars are known to escort as well.