Study recommended for 19 kyu or stronger.(Show more of this level)
The attachement is the most common way to respond.
If black moves towards the top side he can create a wall.
However this wall does contain a lot of aji.
If black plays tenuki, this is also the keypoint for white.
To avoid this result, black can first play a probe.
Black plays tenuki after this move. Later it is likely white will cut.
However it is also possible to continue straightaway for black.