The permanent one-lane mode played on Howling Abyss is ARAM, short for “All Random, All Mid.” It is a five-versus-five League of Legends mode built around a single lane and randomly assigned champions.
Howling Abyss differs sharply from Summoner’s Rift. It has no jungle area, and the entire match is concentrated along one long route, creating constant team fights and making positioning especially important. Players generally cannot freely choose their champion at the start; the roster is selected randomly, with rerolls and a shared bench helping add limited flexibility.
The name is often mistaken for a map name. ARAM is the game mode, while Howling Abyss is the map on which it is played. The other listed choices are different modes: Ultra Rapid Fire changes ability rules and cooldowns, One for All gives a team the same champion, and Nexus Blitz uses a separate compressed battlefield with mini-games.
ARAM also has roots in player-created “all mid” customs before Riot formalized the concept. Its enduring popularity helped make it one of League’s permanent modes.