A full ring is a poker game that includes nine or ten players. This is the standard format still used in many live poker MTTs and cash games.
That said, it has mostly been phased out from online cash games in favor of the faster 6-max format.
For example, the nine distinct positions in full ring poker games are Under the Gun (UTG), Under the Gun +1 (UTG+1), Middle Position (MP), Lojack (LJ), Hijack (HJ), Cutoff (CO), Button (BTN), Small Blind (SB), and Big Blind (BB).