Although a popular etymology connects "hooker" with Joseph Hooker, a Union general in the American Civil War, the word more likely comes from the concentration of prostitutes around the shipyards and ferry terminal of the Corlear's Hook area of Manhattan in the 1820s, who came to be referred to as "hookers".
A streetwalker solicits customers on the streets or in public places, while a call girl makes appointments by phone, or in recent years, through email or the internet.
In escort prostitution, the act may take place at the client's residence or hotel room (referred to as out-call), or at the escort's residence or a hotel room rented for the occasion by the escort (in-call). Although the majority of prostitutes are female and have male clients, a prostitute can be, and have clients, of any gender or sexual orientation.
There are about 42 million prostitutes in the world, living all over the world (though most of Central Asia, the Middle East and Africa lacks data, studied countries in that large region rank as top sex tourism destinations).
Common alternatives for prostitute include escort and whore; however, not all professional escorts are prostitutes.