A Band (腕輪 udewa - bracelet; bangle) is a type of item that appears exclusively in Fire Emblem: Path of Radiance and only from the second playthrough onwards. When equipped they increase certain stat growths. However, you can only equip one band per character. There are a total of 11 of these bands in the game.
Due to the usually free translation works of Nintendo of America, the Paladin Band and Knight Band have their names exchanged from the original Japanese game. 騎士 Kishi means "knight" in Japanese, and is part of the name of the 騎士の腕輪 Kishi no Udewa item listed above, meaning literally "Knight Bracelet". The character that comes with the Knight Band belongs to the アーマーナイト Armor Knight class, which may be the cause to the change of name.