乐土 is a literary term for a 'land of happiness' or 'paradise', often used in classical poetry and formal writing. It carries a poetic, almost utopian feel — different from the everyday word 天堂 (tiāntáng) for 'heaven' or 'paradise'. You'll encounter it in idioms like 世外乐土 ('a paradise beyond the world') or in elevated descriptions of an ideal place.