Balls typically refer to the testicles of a mammal, which are reproductive organs found in males. They are responsible for producing sperm and hormones, and they play a crucial role in the process of reproduction. In human males, the testicles are a pair of oval-shaped organs located inside the scrotum, which hangs outside the body to maintain an optimal temperature for sperm production. In animals, the term may refer to similar structures or may be used colloquially to describe a group of something, such as balls of yarn or balls of fire.