3-6 point pincers
The result is that White has a base, in fact is effectively alive (immediate life). The play at a is a big point, to prevent White being shut in.
Miyamoto Naoki's article at http://gobase.org/articles/miyamoto/ dismisses this pincer, assuming at 3-3 is the only move here.
Below are the two examples of this pincer from GoGoD CD. In both cases the player being pincered rejected the tight play at a and played the shoulder hit at 2. The original pincer at 1 is an unusual move (two cases found in 17000+ games). In both cases it is played from a white position of strength. It is reasonable to assume that the professional players here rejected a as too passive. Imagine both positions if Black plays a and White follows with a play around b, loosely enclosing the small black corner. DaveSigaty