In vitro fertilization, literally translated means an egg is getting fertilized in an artificial environment. This is in contrast to this process occurring within the body. Fertilization is the process of the sperm fusing with the egg and delivering the genetic material. The genetic material from both the sperm and the egg forms the genetic code of an embryo. Practically speaking, in vitro means that your egg must be removed from you. This is very unnatural for an egg, that is also more scientifically referred to as an oocyte. This is normal for sperm since sperm is naturally capable to leave the male body and perform its function outside. For the egg, however, an artificial environment needs to be maintained in order for it to survive outside the female body. Other treatments that are not in vitro fertilization rely on the fertilization occurring within the body and the egg never leaves. This is then scientifically referred to as fertility treatment utilizing in vivo fertilization.