It can vary enormously from table to table depending on your group's vision, which I realize isn't a terribly helpful answer. If we were doing like, the most stock and straightforward xianxia system possible, it would go like:
Realm 0: Qi Condensation
Realm 1: Foundation Establishment
Realm 2: Golden Core
Realm 3: Nascent Soul
Realm 4+: who knows
If I had to phrase it as generically and setting-agnostically as possible, I guess it would probably be like:
Realm 0: Minor supernatural feats; fights will involve one or two techniques at most, unleashed at critical moments.
Realm 1: You are a wielder of supernatural power. Conflicts become exchanges of spell arts.
Realm 2: You are capable of larger-scale miracles and sustained magical exertion. You have largely transcended mortal frailties.
Realm 3: You are an arch-wizard, capable of prodigious supernatural feats and only barely human anymore.
Realm 4: You are a demigod.
Realm 5: You are a god.
Realm 6: You are a cosmic sovereign, treading stars to dust beneath your feet and ruling over hundreds of worlds.