Especially among African Americans, MSM behavior is also known as "being on the down-low". The ex-convict, gangster, and rapper stereotypes are associated with this term. While the male partner of someone "on the down-low" is often aware of the double-life implied by such sexual activity, wives and girlfriends are usually kept from that knowledge. This label is also used in the context of "macho" culture or subcultures for distinguishing between "active" and "passive" sexual partners, where the "active" partner does not usually consider himself to be homosexual.

Oftentimes, sexual encounters between such men occur anonymously. In the US, YMCAs were for many years common places for men to meet other men, while in recent years gay bathhouses and clubs have provided alternative venues for this lifestyle. It is also not unheard of for men who have sex with men to work in the gay porn industry while engaging in heterosexual relationships away from work.

In general, MSM is seen as a wider category that covers both self-identified gay men and other men who engage in same-sex sexual activity.

Sexual behavior in humans is an instinctive form of physical intimacy. It may be performed for the purposes of reproduction, spiritual transcendence, expressing affection, and/or having fun and enjoying oneself (known in this context as "sexual gratification"). The desire to have sex is one of the basic drives of human behavior.

Sexual relationships
Opinions and norms vary about whether an emotional bond of a certain intensity and durability should be a prerequisite for sex (see also below).

Like other primates, Homo sapiens use sexuality for reproduction and for maintenance of social bonds. It is widely believed that children are capable of feeling sexual pleasure, even if they are not yet able to engage in sexual intercourse with each other, and/or are not yet biologically able to reproduce. Yet, child sexuality has historically been severely limited in western societies; in the late 19th century, the hysteria surrounding so-called "self-abuse" (masturbation) among children reached its peak and fueled the adoption of circumcision (including female circumcision) in some cultures.

Many sexual activities can be engaged in by same sex or opposite sex partners. However some, most notably vaginal sexual intercourse, can only be engaged in by partners of opposite sexes. And others, such as tribadism and frication can only be engaged in by partners of the same sex.

As with other behaviors, human high intelligence and complex societies have produced the most complicated sexual behaviors of any animal. Most people experiment with a range of sexual activities during their lives, though they tend to engage in only a few of these regularly. Most people enjoy some sexual activities. However, most societies have defined some sexual activities as inappropriate (wrong person, wrong activity, wrong place, wrong time, etc.) Some people enjoy many different sexual activities, while others avoid sexual activities altogether for religious or other reasons (see chastity, sexual abstinence, asexuality). Historically, most societies and religions have viewed sex as appropriate only within marriage. There is still a widespread belief that sex acts are devalued when engaged in outside of a long-term, monogamous romantic relationship, but extra-marital sexual activity and casual sex became increasingly accepted in modern society during the sexual revolution.