What is the difference between wife and girlfriend???

A girlfriend is one with whom a man has a semi-serious relationship. He might care about his girlfriend, or eventually come to love her. She is a candidate for a wife, but he is not willing to commit to that sort of permanent relationship with her because he is unsure of his feelings. A girlfriend is usually there for fun times.

A man will eventually ask his girlfriend to become his fiancee if he finds that he loves her, and if she is "the one" for him. And his fiancee is the one he may or may not eventually make his wife.

A wife is one to whom a husband has made a commitment, realizing that he loves her and wants to spend every day of his life with her. He wants her to be the mother of his children, his partner, and his mate for life, and she is the one he wants beside him when he dies.