Canonical announced some time ago their Steam Snap which was promoted as stable with Ubuntu 23.04, as they continue to push their own packaging format with Snap but it seems this has been causing problems for Valve.
flatpak - a way to package applications so they have everything they need regardless of the Linux OS you choose (like how Electron packages a web app, e.g. Slack or Discord)
mesa - the graphics layer on Linux; this connects the OS to your drivers
Debian stable - a really stable version of Linux with old software; think Debian Stable = Windows 10/7, and most other distros are like Windows 11; some apps don’t work on Debian because it’s so old, hence flatpak
In case you are curious:
Anyway, I hope you have a fantastic day. :)