STOs and QMs - what exactly are them?

Hello my friends.

I was kicked from a project after a QM request, but after double checking my situation, one of the STOs talked to me and enforced me to stay. I got invited back and received an infinite supply of tasks (yes). I have insanely high rating/rank on this project, so the decision makes sense from their point of view. The QM won't talk to me anymore, but oh well. The three STOs are really nice (everyone likes them) but the QM is very toxic.

Is there a hierarchy between the STO and the QM? What does STO and QM stand for exactly? What are their roles? Are they freelancers like us, or is it a permanent position?

(if anyone is curious: I got kicked by muting voice chat 24/7 as it's in french/german most of the time and I don't understand it as I speak polish/english)