In basketball, you are allowed to take two (2) steps when going in for a layup.
You use it when you are close to the net.
If you are talking about playing basketball, it generally would be a good idea to know how to 'do' a layup. In basketball, the layup is one of the most important shots in the game because most points are scored that way.
The most common shot in basketball is a layup.
Just another way to score