A person with type AB blood is called a universal receiver explain why?

Because, if they need a blood transfusion, they can be given any type that is readily available, with no medical repercussions.

Example:

Type AB can have Type A, because, obviously, Type AB.

Type AB can have Type B, too.

Type AB can obviously take in Type AB, too.

Type O is a universal donor, which means it can give to everyone, so Type AB can take it.