What is the difference between conception and fertilization?

Fertilization is the union of of human egg and sperm cells.

It is uncertain exactly what people may mean by conception. Conception may mean the same as fertilization or it may mean point where the connection is made to the walls of the womb by the zygote. The word does not have a hard definition as it is a debate point between the Pro-Life and Pro-Choice factions about exactly when life begins.