In vitro fertilization (fertilization outside the body) involves harvesting of oocytes ("eggs") which have been stimulated with medications.  These are then inseminated with sperm.  Resulting embryos are then observed and the best embryos transferred back into the woman's uterus.  Remaining embryos can be cryopreserved ("frozen").

A detailed discussion of IVF can be found at ASRM Patient Information Booklet "Assisted Reproductive Technologies".