The Disk Cache SOP Reads and Writes geometry to disk. It can blend between geometry of like topology. Any expression can be used as the Frame Index value giving complete playback control. If the Frame Index goes out of the designated frame range it will wrap around creating a loop. It also supports incremented frame numbers, so you can write out incremental geometry frames and play them back smoothly if Blend Position is enabled.
Any time you want to Write Geometry to disk and Read it back in again especially useful when deformation blur is needed.
Warping time. Slow down or speed up your geometry playback using any expression. Try a sine wave or noise or just keyframe it.
A good way to cache particles for later rendering (Blend Position most likely will not work since particles generally change topology).
-- Jeff Willette