It's a pack that re-enables Piston Translocation from 1.9-1.11
When a piston extends into an entity, it can pull that entity through the piston if there is a valid space for it. Giving a Piston a 0- or 1-tick pulse causes it to ignore this functionality.
If you want to know more, look some stuff up on youtube.

inb4 someone comments about how this be made more efficient: I know. I'm well aware, and I know how to do it. I just haven't yet and this does not cause that much lag.