Mating refers to an advanced form of dating. While dating, you take your girl to restaurants and pay for whatever she cares to ingest. You also take her to plays,movies and other things.
While mating ,on the contrary,you meet a girl, you tell her a shitload of lies about destiny,true love, monogamy, romance and the like, you screw her and never let her see you again.
Barney Stinson: "Hey Aditya, this is my mate for the evening.." points to an attractive girl standing beside him.
Aditya: "your date, you mean"
Barney stinson: "No man!. She is not my date. She is my mate. We are mating."