Systematic Joseki 3-4 5-4 5-3 4-4
Summary - Joseki - The path to avalanche
is usually played when one's planning to start an avalanche or to get some influence in case of a refutation.
Moves Explained
a is the obvious continuation, preventing the cut through.
--- Avalanche is a difficult joseki not only because of its varations, but also due to the fact that White usually ends in gote. For that reason, to play the avalanche, Whit should check that two conditions are fulfilled:
(1) White has a position in the lower right corner (some variations end with White having influence facing that corner - it would be unpleasant if Black could erase it playing some sort of shimari/extension)
(2) Black should not have a stone on the middle hoshi of the upper side - otherwise a group usually created in the small avalanche would be in trouble