Steal the initiative!

White 1 threatens Black's framework link so naturally a connection is in order. However, Black would love to play at A because occupying this point is big. How should Black respond?

Slow!

Black 2 protects the framework link and maximises the local territory, so it seems to be a reasonable option. But after the white 3, black 4 forced exchange, white 5 follows. Black can then encroach a little into White's centre territory but this is scant compensation. Given perfect play on both sides Black will lose by three points.

But Black can do better. See next diagram below.

Sacrifice for tempo!

Black 2 is the answer. It is played as a potential sacrifice. The problem for White is that this stone will require an extra move to capture it. After the white 3, black 4 exchange, White is now the player with the dilemma! If White were now to play the large move at the top, Black can cut off and capture two white stones. So white 5, capturing black 2 is a good option. However this time, given perfect play, Black will win by one point. See next diagram below.

Forcing exchanges

White 7 blocks. Black 8 threatens to capture white 7 so forces white 9. Black 10 threatens to capture two white stones so forces white 11. Black 12 threatens to capture one white stone. After the forcing exchange white 13, black 14, White defends with white 15.

After tidying up the boundary, it can clearly be seen that, by sacrificing one stone to gain tempo, Black has managed to swap a bit of the left side territory for slightly more on the top right.