4-4 point low approach, two-space high pincer with side stone
In the presence of , is a pincer that works in a way that is quite similar to the pincer at a, which has to a great extent replaced in pro games.
For White's reply at b see catenaccio joseki. The hazama tobi at c is the other common possibility.
The usual way for White to play is the immediate 3-3 invasion. is indicated here, because of . may be at a, b or c. At c is often seen in the West because of an 'old information' effect: the pros have hardly played this since 1975, but it's still in the books in English.
This is the modern line. at a instead is bad. Charles Matthews
Allowing white to cut at as a threat to break through could lead to this position. Responding to with a counter hane at a asks for the stone tower tesuji. Black can avoid the stone tower but it will still give w a larger corner, quite likely in sente, for no compensation.
Erikpan: What is the accepted (correct) response to the hane at 3, out of interest?
Slarty: My reading of this is that there is some fight left in this position, it's just to be avoided (by the proper above). Tenuki is good option. Backing off with a one space jump (the point southeast of a) is pitiful but in some ways correct. It's better to play out the stone tower sequence. It's just not a perfect moyo anymore.