Knight's position of two colors
These two stones would make a knight's move if they had the same color. Here, we call them knight's position of two colors.
As an offensive move, it can be referred to as a keima attack.
A natural move here for White is a, the diagonal move, wich simulatenously avoids being pressed (down) at a by Black and threatens to press Black at b. (See Haengma tutorial for beginners)