An all-time low (ATL) means a game is currently cheaper than it has ever been on a given store since we started tracking it. ATLs are the strongest signal a discount is a real deal rather than a manufactured "sale".
Wishlist managers like to wait for ATLs before pulling the trigger. We surface every ATL we detect — across Steam, Instant Gaming, Gamivo, Green Man Gaming, Kinguin, YuPlay, GOG, and Fanatical.