I think it's essentially half of what Echo does. Echo has to do two separate tasks [1]: The first is to figure out exactly what direction your voice is coming from. Once it has a direction, uses beamforming [2] to get a higher SNR for your voice. These two processes (probably) happen simultaneously.

The beamforming in Pulse Audio is simply the second half of this process. Given a microphone array and a desired direction to listen in, it can control the pickup pattern of the array by delaying the signals from each mic differently.

1: I haven't really studied how Echo works, so these are mostly assumptions. 2: https://en.wikipedia.org/wiki/Beamforming