It's kinda like root-ish privileges. It facilitates doing things that you're not technically prohibited from accessing, but there simply is no interface for. It uses administrative console commands (administrative in the management sense, not like administrator=root sense) to execute changes that don't have any pathway built-in for the end-user.

Personally, nearly all my devices are rooted, but I did use Shizuku for some accessories on a few devices. It's a bit of ado to setup; not difficult just a handful of steps. Worth it if you really need or want to do something the GUI won't provide and you'll likely find more uses down the line.