Fallout 4 Ppf.esm ~repack~

Fallout 4 uses a system called to improve performance. It takes multiple static objects (like a wall, a door, and a chair) and combines them into one mesh. Previs is a map that tells the engine, "If the player cannot see this, do not render it."

It should always be near the top of your load order, right after the official DLCs and the Unofficial Fallout 4 Patch (UFO4P). Fallout 4 Ppf.esm

In short:

(Place high, usually right after the unofficial patch) (Other Masters and Mods) Fallout 4 uses a system called to improve performance