Curses are Auras that enchant players rather than their permanents, saddling the enchanted player with an ongoing disadvantage or making them a particularly appealing target in Commander. Curse decks pile these enchantments onto opponents and reward you for keeping them around.
Lynde, Cheerful Tormentor can recur destroyed Curses and move them back onto opponents, while Curse of Disturbance encourages the entire table to attack one unfortunate player. Cards such as Trespasser's Curse instead punish opponents for simply developing their own battlefield.