Fertilization is the impregnation, the state when a sperm cell penetrates the egg cell and the genetic material of both cells combines.
A few days after fertilization implantation happens. Implantation is the attachment of the fertilized egg to the uterus, happens on average about 9 days after ovulation/fertilization (between 6 and 12 days) and is required for the fetus to continue to grow.
