With 1 black creates an asymmetrical situation in the corner thus giving the development a natural direction of continuation: along the left side of the board. The reason that the left side is more important than the lower side is that black 1 is on the fourth line of the left side and on the third line of the lower side.

Black's continuations

If black continues here he can either play a tight move with A or B, a slightly less tight move with C or D, or play a large scale move with E or F.

White's continuations

If white decides to continue locally he will attack the corner with either A or B. Both moves will be discussed in great detail.
When settling locally is all what white wants then white will approach with A but in general white will choose the high move B. In some (special) circumstances white will approach the corner from a larger distance with C or D. These moves will however not be discussed in this joseki introduction.

As mentioned before black 1 intends to make a corner enclosure (with any of 2, 3, 4 or 6). White 2 prevents such an enclosure and at the same time attacks the corner stone. If black wants to settle the corner quickly the attachment with 3 is the recommended method. In return for the corner territory white gets a position along the left side with either A or B. The exact location of this move will depend on the global situation on the board and especially the situation in the upper-left corner. Please study the professional games to get an understanding of how to choose between these options.

But what can white do after black 3 when he would like to develop the lower edge? The answer is the rather crude move of 4. This move triggers one of the most complicated joseki known in Go today: the nadare (Japanese for avalanche, because of the white stones [snow] gliding over the black [rocks]).

This joseki is far too complicated to discuss here. I give three examples to illustrate what might happen. The variation shown here is maybe the most simple variation possible: black takes the corner and white achieves his aim to develop the lower side.

But things are not that simple unfortunately. Please see the next diagram.

Just to show you how complicated things can get I include this variation. The result is that black develops a position along the lower side and white along the left side. Both sides are very strong and these two positions of thickness will strongly affect the fighting on this part of the board.

The nadare is a so called large scale joseki with many variations spreading over the board and affecting the game as a whole. The next diagram illustrates this with a final example of what might happen in this joseki.

This variation is the main line of the o-nadare (large avalanche). Black gets the corner and in return white gets a position along the left side and in the center. The white and black group in the center will be the main focus in the rest of the game and the evaluation of this joseki will strongly depend on the situation in the lower-right and upper-left corner.

But please forget about these variations! You don't need to play this joseki. When I asked Takemiya Masaki about this joseki he said:

"I will never ever play nadare in my life again. I don't like large scale joseki since it's complicated and it settles too much of the board.
For beginners as white I recommend just to play the simple variation as shown in pattern 2.1."
(And as black choose either 2.1.1 or 2.1.2, both variations are reasonably straightforward and sente [editor]).

Now let's return to the joseki in diagram 4,3-a-1:

If extending along the left side one point further is of valuable to white (for example, because white 8 has some extra meaning for the upper-left corner) then white can play 6 instead of the solid connection enabling him to extend to 8.

In the two previous diagrams black's position along the lower side of the board is very solid and low making it uninteresting and not urgent for both players to play there for a while. If black wishes to make the lower side interesting (maybe because the right corner has a black position) then black will choose to play keima with 3. White can settle the kakari stone with the sequence through 8.

So far black played very simple and rather passive. But what happens when black starts a fight by attacking the attacker with for example black 3?

Black 3 is called a hasami (pincer) and usually leads to more complicated developments since white usually cannot easily settle his group and consequently fighting starts. The recommended way to play here is white 4 which triggers a sequence which settles the white shape in exchange for black territory along the lower side of the board.

In this variation black plays 7 to keep white out of the corner. In return white gets the very pleasant atari at 8. The result is that black takes some territory while white gets a strong position on the outside and sente.

Black 3 is more severe than the pincer which was discussed in the previous diagrams. White's kosumi at 4 prevents black from connecting at 9. White wants to follow up the move at 4 with another stone at 12 thus developing the lower side. Black 5 prevents this. White 6 takes the 3,3 point and the consequential moves show an exchange: black takes territory on the left side while white 14 neutralizes black 5 and establishes some thickness along the lower side of the board.

If black answers white 6 by blocking it with black 7 white will take the initiative along the left side by pressing with 10.

The next couple of variations will discuss the low approach by white with 2. Usually this move will make it easier for white to settle locally and consequently the variations are a little easier compared to the high approach move.

This variation shows a typical result: black develops along the lower side while white settles his group along the left side.

Because white 2 is low it is difficult for black to prevent that white makes a base for his group. For example, black 3 here prevents that white plays there but white 4 and 6 settle the white group anyway. In the final position white can still play A or B and so is ensured of enough space to live.

In this variation black attacks white 2 by playing 3. White settles his group quickly with the kosumi at 4 and after black defends with 5 (against white A), white slides to 6 thus ensuring life. Black 7 extends along the lower side to defend against a white move at B.

The final variation in this line is when black attacks white 2 with the most severe move at 3. White uses an interesting technique here: by attacking black 1 white builds up enough power to eventually neutralize black 3.