Of the ovum by sperm occurs, usually, in the ampulla of fallopian tube.
Involves chemical attraction of the sperm to the ovum by substances produced by the ovum, adherence and penetration of the membranous structure around the ovum, the zona pellucida, and adherence of the sperm head to the cell membrane of the ovum with breakdown of the areas of fusion and release of the sperm nucleus into the cytoplasm of the ovum.
While millions of sperm are deposited into the vagina with intercourse, only 50-100 sperms reach the ovum and the zona pellucida.
Sperms bind to a receptor site in the zona pellucida and the lysosome like organelle in the head of the sperm, the acrosome, breaks down.