From The Art and Popular Culture Encyclopedia
A pimp finds and manages clients for prostitutes and engages them in prostitution (in brothels in most cases and some cases street prostitution) in order to profit from their earnings. Typically, a pimp will not force prostitutes to stay with him, although some have been known to be abusive in order to keep his prostitutes in line or to maximize profits. A pimp may also offer to protect his prostitutes from rival pimps and prostitutes, or from abusive clients. He can also enable a prostitute to work in a particular area under his control. Pimping is a sex crime in most U.S. jurisdictions.
Most people who work managing prostitutes are men, but some women work in this capacity as well, though rarely in street prostitution. Women are rarely called pimps, as the word implies male dominance (see Pimps in Popular Culture below) - a woman who manages prostitutes is generally called a mamasan or a madam. (This should not be confused with the title of respect given to adult women in most English-speaking countries.)
Often, low level pimps will initially present themselves as lovers or father-figures to prostitutes (who may be run-aways or otherwise lack a family network) before introducing them to prostitution and perhaps drug addiction. This practice is called "turning out." Most pimp-prostitute relationships are suggestive and guided while others are abusive, using psychological intimidation, manipulation and physical force to control the members in the "stable".