What crucial advice does Jethro provide and how does it affect Moses and the Israelite's?

Yitro (Jethro) advised Moses to appoint judges and officers, to assist in conducting the affairs of the Israelite nation (Exodus ch.18). This became a national institution, continuing for centuries, as alluded to in various verses in later books of the Hebrew Bible. There were leaders of ten, leaders of fifty, leaders of one hundred and leaders of one thousand. They provided adjudication, advice, leadership in war, Torah-teaching, and overall supervision.