In men, fertility means the ability to make a woman pregnant. To do this, the man's reproductive system needs to produce, store and release sperms. They also need to be transported outside of his body and deposited in the vagina - such sperms should find their way to the uterus to meet with the egg which has been released from her partner's ovaries not more than 24 hours earlier. One can imagine why timing is so important in this area.
It is a MYTH to think that any woman will get pregnant just by having sex with a fertile male at any time during her menses cycle.
The organs that produce sperms are called the testes. Normally a man has two testes, located in the scrotum, the pouch of skin that hangs behind the penis. Each one is called a testis (or testicle). Inside each testis are very fine tubes called the seminiferous tubules. This is where sperm are manufactured. (It is estimated that a normal male produces about 50 to 200 million sperms a day).
Unlike a woman, who is born with all the eggs (finite number of eggs) she will have in her life, a man makes new sperms continually. Once a man passes through puberty, his stock of sperms is refreshed about every 72 days.