Answer:
In simple words, The Jews became monotheists — they trusted inside and praised only one deity. This sticks out for scholars, since monotheism was exceedingly rare in the middle ages. Many ancient cultures were polytheism — they claimed and worshipped many gods.
Monotheism seems to be the religion of one divine entity. The background of monotheism seems to be the past of human civilizations adjusting their values to a evolving environment, mostly from polytheism towards henotheism once again to monotheism.