ICSI (Intra Cytoplasmic Sperm Injection) is a specialised procedure to form an embryo in the laboratory in which a sperm is directly injected into the ovum placed in a nutrient broth.
GIFT (Gamete Intra Fallopian Transfer) is a method to transfer an ovum collected from a donor into the fallopian tube of another female who cannot produce one, but can provide suitable environment for fertilisation and further development. ZIFT (Zygote Intra Fallopian Transfer) is a method (similar to in vitro fertilisation and embryo transfer) in which the zygote (early embryo) up to 8 blastomeres is transferred directly into the fallopian tube.
ET (Embryo Transfer) is a method in which the fertilisation is done in vitro and the formed zygote is transferred into the uterus of the female who cannot conceive.