Yes, I think I know. A tier means what rank a film is. Like if you gave one movie 100/100 it'd probably be a tier ten. I think you need to have ranked at least ten or so films before they start dividing them up into tiers.
In case you're interested, a few other NHC members have them. Theresalwaysabiggerfish is The Comedian, Wbadger is Wbadger, and I think TFD and Jake have accounts but I'm not sure what their usernames are.