Sex is a biological term that refers to the reproductive functions of living organisms. It typically involves the exchange of genetic material between two individuals in order to produce offspring. In humans, sex is typically associated with sexual intercourse, which is the physical act of two people coming into sexual contact with each other in order to reproduce.
Whether sex is necessary is a subjective question and depends on an individual's goals and values. Some people may consider sex to be an important part of a romantic or committed relationship, while others may not place as much importance on it. Some people may also choose to abstain from sex for personal, moral, or medical reasons. Ultimately, the decision about whether or not to engage in sex is a personal one and should be made based on what is best for the individual.