A sex worker is a person who provides sex work, either on a regular or occasional basis. The term is used in reference to those who work in all areas of the sex industry. According to one view, sex work is voluntary "and is seen as the commercial exchange of sex for money or goods". Thus it differs from sexual exploitation, or the forcing of a person to commit sexual acts.

The term "sex worker" was coined in 1978 by sex worker activist Carol Leigh. Its use became popularized after publication of the anthology, Sex Work: Writings By Women In The Sex Industry in 1987, edited by Frédérique Delacoste and Priscilla Alexander. The term "sex worker" has since spread into much wider use, including in academic publications, by NGOs and labor unions, and by governmental and intergovernmental agencies, such as the World Health Organization. The term is listed in the Oxford English Dictionary and Merriam-Webster's Dictionary.

The term "sex worker" is used by some types of sex workers (i.e. prostitutes) to avoid invoking the stigma associated with the word "prostitute". Using the term "sex worker" rather than "prostitute" also allows more members of the sex industry to be represented and helps ensure that individuals who are actually prostitutes are not singled out and associated with the negative connotations of "prostitute". In addition, choosing to use the term "sex worker" rather than "prostitute" shows ownership over the individuals' career choices. Some argue that those who prefer the term "sex worker" wish to separate their occupation from their person. Describing someone as a sex worker recognizes that the individual may have many different facets, and are not necessarily defined by their job.

The term is strongly opposed, however, by many who are morally or politically opposed to the sex industry, such as social conservatives, anti-prostitution feminists, and other prohibitionists. Such groups view prostitution variously as a crime or as victimization, and see the term "sex work" as legitimizing criminal activity or exploitation as a type of labor.

Sex work can take the form of prostitution, stripping or lap dancing, performance in pornography, phone or internet sex, or any other exchange of sexual services for financial or material gain. Sex workers who include sexual intercourse as part of their services are considered full-service sex workers. The variety in the tasks encompassed by sex work leads to a large range in both severity and nature of risks that sex workers face in their occupations. Sex workers can act independently as individuals, work for a company or corporation, or work as part of a brothel. All of the above can be undertaken either by free choice or by coercion, or, as some argue, along a continuum between conflict and agency. Sex workers may also be hired to be companions on a trip or to perform sexual services within the context of a trip; either of these can be voluntary or forced labor.

Sex workers may be any gender and exchange sexual services or favors for money or other gifts. The motives of sex workers vary widely and can include debt, coercion, survival, or simply as a way to earn a living. Sexual empowerment is another possible reason why people engage in sex work. One Canadian study found that a quarter of the sex workers interviewed started sex work because they found it "appealing". The flexibility to choose hours of work and the ability to select one's own client base may also contribute to the appeal of sex work when compared to other service industry jobs. Sex work may also be a way to fund addiction. This line of work can be fueled by an individual's addiction to illegal substances before entering the industry or being introduced to these substances after entering the industry.

For camming services, motivations can vary when engaging in sex with real-life versus virtual partners. A 2023 study found that sex workers providing camming services were more likely to engage in sex with virtual partners for resources and specific types of sexual experiences (e.g., kink). In contrast, they engaged in sex more often with real-life partners for physical pleasure, motivated by the physical desirability of their partner, and to express love and commitment. However, for many other motivations, such as stress reduction, self-esteem boost, emotional expression, or utilitarian reasons, there were no significant differences in frequency of engagement with real-life versus virtual partners.

These motives also align with varying climates surrounding sex work in different communities and cultures. In some cases, sex work is linked to tourism. ^{[citation needed]}