Short answers, pulled from the story.
Monolatry describes a specific religious stance where many gods exist yet only one receives worship. Frank E. Eakin, Jr. wrote in 1971 that Jews believed other gods existed but trusted their own deity to protect them.
Pharaoh Akhenaten began his religious reforms during the fifth year of his reign around 1348 BCE. He initially ruled as Amenhotep IV before changing his name to Agreeable to the Aten and built the new capital city at Amarna which stood as Horizon of the Aten.
Historians argue that early Israelites practiced forms of monolatry or henotheism because Exodus 12:12 references gods of Egypt suggesting their existence was acknowledged by the Israelites. John L. McKenzie noted that divine beings existed universally without question in the ancient Near East while books like Hosea and Nahum lamented apostasy from polytheistic cults during the eighth century BCE competition with Baals.
The shift from monolatrous practices toward strict monotheism occurred during the Babylonian captivity period when many Israelites chose foreign gods over Yahweh before the sixth century BCE. Evidence within the Hebrew Bible records many Israelites worshipping idols instead of Yahweh before this era and Rashi recognized in his eleventh-century commentary on Deuteronomy 6:4 that belief in one God was only part of faith at Moses' time.
Joseph Smith taught in 1820 that he saw two personages including God the Father and Jesus Christ. By 1843 he stated these beings possessed separate tangible bodies unlike traditional Christian views and Latter-day Saints believe three distinct beings belong to one Godhead united in thought and purpose.