Short answers, pulled from the story.
Amun was a major ancient Egyptian deity first attested in the tomb of Pharaoh Unas around 2350 BCE. He began as a member of the Hermopolitan Ogdoad and rose to become patron deity of Thebes and, on his own, king of the gods. His name, written imn, meant something like "the hidden one" or "invisible."
The name Amun, written imn, meant something like "the hidden one" or "invisible." This meaning is reflected in a Pyramid Texts epithet that calls him "the great god whose name is unknown."
Amun-Ra was the fusion of Amun with the sun god Ra, formed after Amun gained national importance under Ahmose I in the 16th century BC. As Amun-Ra he was a transcendental, self-created creator deity and held chief importance in the Egyptian pantheon throughout the New Kingdom.
Amun gained the ram after Egypt conquered Kush and identified the ram-headed Kushite chief deity as Amun. Because rams symbolized virility, he also became a fertility god, absorbing the god Min as Amun-Min. The resulting Horns of Ammon later appeared on coins of Alexander the Great.
The Theban High Priests of Amun were effectively the rulers of Egypt from 1080 to about 943 BC. The priesthood owned two-thirds of all temple lands in Egypt and 90 percent of her ships, making them as powerful as the pharaoh, if not more so. Herihor became the first ruling High Priest in 1080 BC.
Akhenaten, also known as Amenhotep IV, advanced worship of the Aten, defaced symbols of older deities, and moved his capital away from Thebes, leaving the priests of Amun without their former power. Worship of Amun-Ra was restored under Akhenaten's son, who reversed Atenism and renamed himself Tutankhamun.
When Alexander the Great occupied Egypt in late 332 BC, the oracle at Siwa pronounced him son of Amun, and his coins later showed him wearing the Horns of Ammon. The Romans named ammonium chloride from deposits near the Temple of Jupiter-Amun sal ammoniacus, the root of ammonia, and spiral-shelled ammonites are likewise named for Amun's horns.