UPK files, packages

Are those discontinued? Do i have to know anything or they are hidden, or now they are automatic? Pls some links or short intro if you can.

UPK files aren’t used anymore. They were replaced with uasset files.

UPK file:

used in UDK
was a package with several assets in it

Your content files are now stored in a specific project folder, usually in Documents/Unreal Projects