Prostate is a gland responsible for producing semen, the fluid that carries the sperm in people with penises. The prostate is about the size of a walnut and is located in front of the rectum, at the neck of the bladder and the urethra (the tube that carries urine outside the body). Stimulation of the prostate is also responsible for sexual pleasure.
Sources:
https://medlineplus.gov/prostatediseases.html
https://www.webmd.com/sex/prostate-orgasm-what-it-is
https://www.hopkinsmedicine.org/health/wellness-and-prevention/overview-of-the-male-anatomy