The fork trick is a well known trap in the opening. It is important to know. It sacrfices a knight for a center pawn and then forks two pieces, regaining the material with a better position:
Although this trick doesn't gain any material, white will a good game and an easy win. The try Bxf2?! is not much better besides exposing white's king a puny bit. It is a good trick to know, especially in the Four Knights where it occurs very often.
Hope you like it. Enjoy!