In all probability Amun originally was a god of the air; his name means "the hidden one". One of the ways in which he was invoked in the New Kingdom was "Lord of the Breath of Life".
The god was especially linked to Thebes, where he rose enormously in importance during the Middle Kingdom. Here he was part of a triad with his consort Mut and their son Khonsu. But Amun also had links with other important gods, for example with the sun god Re in the frequent appellation Amun-Re.
Because of the political rise of Thebes, its deity Amun was able to become king of the gods (Amonrasonther, in Egyptian Imen-Ra nesut netjeru, "Amun-Re, king of the gods"). And as the power of the king was waning at the end of the Ramesside Period, a divine state was created in Thebes under the leadership of Amun.
In Hermopolis the primeval Ogdoad (group of eight gods) had Amun as one of its members; he and his female counterpart Amaunet represented the hidden element. Through priestly speculation Amun became the chief god and even the begetter of the Ogdoad, which was then considered to be the shape of Amun.
Amun is usually depicted as a man, wearing a headdress with two tall feathers and a ribbon hanging down his back.