Definition:
Insemination is the deliberate introduction of sperm into a female animal or plant for the purpose of impregnating or fertilizing the female for sexual reproduction. The sperm is introduced into the uterus of a mammal or the oviduct of an oviparous (egg-laying) animal.
For more info,
In mammals, insemination normally occurs during sexual intercourse, but insemination can take place in other ways, such as artificial insemination. Each form of insemination has legal, moral and interpersonal implications. Whether insemination takes place naturally or by artificial means, however, the pregnancy and the progress of it will be the same.
Insemination may be called in vivo fertilisation (from in vivo meaning "within the living") because an egg is fertilized inside the body, and is thus essentially the opposite of in vitro fertilisation.