The sperm is the male reproductive cell and the egg or ova is the female reproductive cell.
Sperm and egg fusion:
Normally only one sperm can enter an egg.
The reason is when one sperm comes in contact with the zona pellucida of an egg, the changes in the egg membrane don’t permit other sperm to enter further, blocking polyspermy.
The fertilisation of an egg with two sperms is rare and occurs in around 1% of cases. The developing embryo usually does not survive in this condition.