The spirits of the dead are being judged by Yama and his followers (called 'Yamadutas') according to their good and bad deeds. They are supposed to either pass through a term of enjoyment in a region midway between the earth and the heaven of the gods, or to undergo their measure of punishment in Naraka (or Jigoku), the nether world, situated somewhere in the southern region. After this time they return to Earth to animate new bodies following the theory of reincarnation.
Yama is also the lord of justice and is sometimes referred to as Dharma, in reference to his unswerving dedication to maintaining order and adherence to harmony. In this capacity, he is normally depicted wearing a Chinese judge's cap in Japanese art. It is said that he is also one of the wisest of the devas. In the Katha Upanishad, among the most famous Upanishads, Yama is portrayed as a teacher.
In art, he is depicted with green or red skin, red clothes, and riding a buffalo. He carries a rope lasso in his left hand to carry the soul back to his abode called 'Yama-loka' . In Buddhism, the Wheel of Life mandala is often depicted between the jaws of Yama. Garuda Purana mentions Yama often. His description is in 2.5.147-149: "There very soon among Death, Time, etc. he sees Yama with red eyes, looking fierce and dark like a heap of collyrium, with fierce jaws and frowning fiercely, chosen as their lord by many ugly, fierce-faced hundreds of diseases, possessing an iron rod in his hand and also a noose. The creature goes either to good or to bad state as directed by him."
He is a Lokapala and an Aditya and one of the Ashta-Dikpalas representing the south. He is the son of Surya (Sun) and twin brother of Yami, or Yamuna, traditionally the first human pair in the Vedas. He was also worshiped as a son of Vivasvat and Saranya. His wife is Syamala. He is the father of Yudhisthira, the oldest brother of the 5 Pandavas (Karna was born prior to Kunti's wedlock, so technically Karna is Yudhthira's older brother) and is said to have incarnated as Vidura by some accounts in the Mahabharata period. He reports to Lord Shiva the Destroyer, an aspect of Trimurti (Hinduism's triune Godhead). Three hymns (10, 14, and 35) in the Rig Veda Book 10 are addressed to him.