Can't find a workspace

Hi all!!

There is something that I don't entirely understand and is why some people is member on a certain sharepoint site and they cannot find the workspace into PowerBI web.

I think it may be because they have member permissions but they aren't member of the group, but this is what I don't understand and I want you if you can explain it to me as a mortal simple person 🙂 

Far away from sharing to me links to read a big post, if someone could explain it to me, I would be grateful.

Thanks in advance! 🙂