It's been two years

@odium @SirLotsaLocks based on the name and my knowledge about wayland, I think it allows fullscreen programs to directly render to the buffer that will be shown on the screen instead of having to first render to some other buffer and then have kwin copy it to the one that will be displayed on the screen.
Note that this is a 2 year old post about Plasma 5.21 so you probably already have a newer version of Plasma installed.