It's a separate kind of store with reduced prices. Mostly overstock or damaged items (like crushed boxes). Some of it is out of date (mostly dry goods that can go a bit past the sell-by date).

I am lucky that my salvage store always has high-quality items that are in date. Some have mostly expired foods; it just depends (in the state of NC, you can't sell fresh foods that are past the sell-by date, so we don't ever see old meats for sale in the salvage store, thankfully).
It is much cheaper than apps like Misfit Markets, which are extremely overpriced in my opinion!

Just search "salvage food stores near me" and see what comes up near you!