Developer-Dude It requires a work profile management app. It's normally an app remotely managing it for a company to deploy profiles managed by them on devices not owned by them where they essentially own the profile but can't do much with the overall device beyond certain specific things like password policy enforcement. People talking about it with GrapheneOS normally mean using a fully local, open source app such as Shelter for managing it yourself. With a local management app, it's similar to a Private Space but with a UI depending on an app for managing it and less built into the OS for it since it's meant to be managed by an app rather than directly by a user. You can essentially use a work profile as a 2nd Private Space in Owner. The features supported compared to a Private Space largely depend on what the management app provides.
Private Space has separate encryption keys similar to a secondary user with Weaver throttling. Work profiles have some separation for it but it's half-baked and wasn't really ever completed. Private Space is closer to a secondary user with better separation in several other ways too. Private Space is pretty much a nice nested secondary user while work profile are only part of the way there. If it was possible to make more than one Private Space per profile then work profiles would be obsolete for local usage, but it's currently useful for stuff like making a dedicated profile for sandboxed Google Play while still having Private Space for the intended purpose of sensitive data.