The prostate is actually not one but many glands, 30-50 in number, between which is abundant tissue containing many bundles of smooth muscle. The secretion of the prostate is a milky fluid that is discharged into the urethra at the time of the ejaculation of semen.
The origin of the name "prostate" is quite curious. The word is from the Greek "prostates", to stand before. The anatomist Herophilus called it the prostate because, as he saw matters, it stands before the testes.