Resets some Blood Vial and Bullet pickups, and Antidotes and the one spot where you get 5 Sedatives. Shards, coldbloods, those two bold hunters marks, weaponized consumables like molotovs don't get restored though. It doesn't respawn one-time enemies, hunters or bosses either.
Honestly a waste of echoes unless there's some super-secret about it that none of us know about.