Hens produce a class of antibodies called IgY whose natural role is to protect the chicken and the growing chick inside the egg. The overall structure of the IgY molecule is similar to mammalian immunoglobulin. Egg yolk antibody (IgY) can be a suitable alternative to IgG due to its unique characteristics, cost-effectiveness, and compliance with the ethical principles of working with animals. The process of immunization of chickens, production of specific antibodies against antigens, and purification of IgY is called IgY technology. In this review article, we will investigate how to produce IgY antibodies, immunization in chickens, various methods of antigen administration (muscular, subcutaneous, intravenous, etc.), IgY extraction from egg yolk, and its purification. Finally, some diagnostic and therapeutic applications of this antibody have been investigated.