The term's definition can vary depending on the person or on the age group.
It can range from acts that involve kissing, oral sex, or intercourse.
During the twenty-first century paid sex was not considered to belong to the category of casual sex; however, in the 1900s-1930s there was more to paid sex than simply the exchange of money–it was a contact between humans without the ties of a relationship.
Technological advancements such as the automobile and movie theaters brought young couples out of their parents' homes, and out from their watchful eyes, giving them more freedom and more opportunity to engage in sexual activity.
At colleges, hookups are common between students at parties, in dormitories and fraternity houses, at surrounding bars and clubs, and at popular student vacation destinations.
For example, a study of Canadian college students who planned to hook up while on spring break showed that 61% of men and 34% of women had sex within a day of meeting their partner.
On the other hand, hook up culture is thought to be oppressive and monolithic, with intimacy only occurring within a specific context.
As a result, Garcia and other scholars argue that young adults are able to reproduce physiologically but are not psychologically or socially ready to 'settle down' and begin a family.
The term "hooking up," meaning an instance of casual sex, differs from hook up culture.
A hook up is an act that involves sexual intimacy, claimed by many to be a sexually liberating act.
These developmental shifts, Garcia's systematic review of the literature suggests, is one of the factors driving the increase in hookups, a "popular cultural change that has infiltrated the lives of emerging adults throughout the Western world." The review shows that hookups are becoming increasingly normative among young adults and adolescents in North America and have taken root throughout the Western world, which represents a notable shift in how casual sex is perceived and accepted.
Garcia and others have noted that the "past decade has witnessed an explosion in interest in the topic of hookups, both scientifically and in the popular media.