An oocyte is a female germ cell involved in reproduction. It is the precursor to an egg cell and plays a crucial role in the process of fertilization. Oocytes are produced in the ovaries and undergo several stages of development before they can be released during ovulation. During fertilization, a sperm cell from a male combines with an oocyte to form a zygote, which eventually develops into an embryo. The quality and health of the oocyte are vital for successful conception and pregnancy, making them an important focus in fields like reproductive medicine and fertility treatments.