From the README:

A Steam Deck plugin for the Decky Plugin Loader that makes it possible to pause and resume games even for those that don’t have an immediate pause option.

Useful for when you wish to temporarily suspend an application in order to redirect the cpu and gpu ressources to another without having to close it.

Since used RAM and VRAM won’t be able to be recovered from paused apps you might look into tweaking your swapfile to make things smoother: https://github.com/CryoByte33/steam-deck-utilities

It sends the SIGSTOP signal to all the children of the reaper process to stop the execution and SIGCONT to resume them. (Signal (IPC))