Bayonet Attack generally refers to an opening in which one side plays g2-g4 or g7-g5. This move has many pros and cons. It can attack knights on f6, control the g file, and gain control of other squares. Cons include an early weakening of the kingside, and losing control of many squares. A common example of this opening is in the Caro-Kan:
The move g4 there is not very good due to the fact that the pawn is weak, and it doesn't really do much. Hope you had fun reading and feel free to comment.