[1] Depending on the game, a set may consist of two cards of equal rank (a "pair") as in Bieten, three of a kind as in poker, or more.
A set or group comprises 3 or 4 cards of the same rank and, usually, different suits.
A prial, pair royal, gleek or triplet is a set of 3 cards of equal rank and a quartet or, in some older games, a mournival, is one of four cards of the same rank.
[2] Usually a pair (2 cards of the same rank but different suits) is not counted as a "set"; but some games, such as Bieten or Perlaggen do include pairs as sets.
[3] In Texas Holdem poker, a set refers to a three of a kind where the player has a pocket pair.