This short Ableton tutorial walks through the Groove Pool from start to finish: what it is, where to find it, and how to put it to work. The Groove Pool is a dedicated section of Live's interface where you store groove files that can then be applied to MIDI or audio clips to shift their timing and feel.
Grooves live in the Core Library under Swing and Groove, and you can load several into the pool at once. From there, each clip in your set can be assigned its own groove independently, giving you fine-grained rhythmic control across a full arrangement.