3-4 point high approach, two-space high pincer, keima
After Black's outside attachment, White will eventually have to live on the side, while Black takes central influence. Next Black can aim at attacking White's other group. This fight has been regarded as favourable for Black in most circumstances, a.o. by Ishida's Joseki dictionary.
Each of Black's moves , and are sente and cannot be answered by a hane: each cut will be favourable for Black. In the end, White cannot even play at , so Black takes a big corner. All the cannots'' in the above explanation can be explored further.
This variation has been played for 20 years, and is popular right now in pro games. is a common tesuji.
Up to is a common continuation in recent pro games. and can be played in a different order. (17 games out of 47 in a gobase search on this position) Most variations are about : it is seen at a, b', c and d. is seen at a and z.
This is not tesuji. Black is split into three groups.
3. White peacefully plays atari (not recommended)
This peaceful result can easily be visualized. Black takes a substantial amount of territory. White takes influence and sente. However, it is felt that is not placed effectively. In fact, there is a joseki resulting from the ogeima variation where is instead at a. That result is considered even and the final judgment will depend on whole board strategy or personal preference.
There are a few games in which Black fiercely plays . After , White can retreat at a or fight at b. These fights then spread over the whole board.
There are also a few games where - is exchanged, resolving into the main variation again. That leads to the question why at a is tesuji at all.