The testicle is a part of the male reproductive system, and each biologically male person has a set of two testicles. They are round and are contained in the scrotum under the penis. They come in pairs and lay outside of the body, for the purpose of keeping them cooler than the rest of the body. They are responsible for producing sperm to fertilize eggs and start reproduction. I think that's all you need to know
(No picture because I want to keep my history clean and am too lazy to use a proxy)