At the moment there are 4 categories of items in the game:
Activation specifies when exactly an item is used. There are 4 types of activation:
On start
Activates once when the fight starts
On hit
Activates when a player receives damage from an item of Melee Weapon or Ranged Weapon category
On cooldown
Activates every X seconds, specified in the item’s description under Cooldown
On attack
Activates when a player successfully attacks the opponent with Melee Weapon or Ranged Weapon