MusicTechHelpGuy demonstrates region automation in Logic Pro, using Retro Synth's mod wheel controlled filter cutoff as the example.
Recording the mod wheel live while playing gives you natural, performed filter sweeps captured as real-time automation on the track.
Switching to region automation lets you draw CC1 (mod wheel) shapes by hand instead, opening up movements that would be tricky to play live, like a clean sweep from fully open to fully closed.
Splitting a part into separate regions means each one holds its own independent mod wheel automation. Copy or repeat a region and its automation comes along with it, which makes building varied, repeatable filter movements across a part fast and precise.