Member vs Registered User

I noticed that someone posting here has “Registered User” written under their name where everyone else has “member” displayed. They posted today in a current thread, so it’s not like the whole “guest” thing you see in old threads. What’s the difference between “member” and “Registered User”?
(I did not mention the poster’s name as I don’t know if this is some sort of disciplinary action that I don’t know about, and I didn’t want to draw attention to this person.)