Medium Armor Sets ESO. Medium Armor Sets in the Elder Scrolls Online offer mostly Stamina-based bonuses and used in Stamina DPS Builds.
Light Armor Sets in the Elder Scrolls Online offer mostly Magicka-based bonuses and used in Magicka DPS or Healer Builds.
Arena Weapons in ESO are special ability Altering Weapons – Sets, you can get from the Maelstrom, Dragonstar and Blackrose Prison Arenas.
3 Piece Item Sets are special Armor Sets in The Elder Scrolls Online that offer bonuses for up to 3 items only.
Monster Sets in the Elder Scrolls online are special 2-piece Armor Sets that offer unique and strong bonuses.