Jethro, also called Reuel, was a priest of Midian. He became father-in-law to Moses when his daughter Zipporah married him.
Moses spent forty years of his life with Jethro tending to his flocks. It is very likely that Moses learned more than shepherding during this time though, because in later years Jethro provided Moses some very valuable advice in governance. This took place when the Israelites were encamped at Sinai. Jethro came to meet Moses along with Zipporah and her two sons, whom Moses had deposted in his care. The following day, Jethro witnessed how Moses was bogged down in adjugating civil cases and counselled Moses in the art of delegating.
Moses' father-in-law replied, "What you are doing is not good. You and these people who come to you will only wear yourselves out. The work is too heavy for you; you cannot handle it alone. Listen now to me and I will give you some advice, and may God be with you. You must be the people's representative before God and bring their disputes to him. Teach them the decrees and laws, and show them the way to live and the duties they are to perform. But select capable men from all the people-men who fear God, trustworthy men who hate dishonest gain-and appoint them as officials over thousands, hundreds, fifties and tens. Have them serve as judges for the people at all times, but have them bring every difficult case to you; the simple cases they can decide themselves. That will make your load lighter, because they will share it with you. If you do this and God so commands, you will be able to stand the strain, and all these people will go home satisfied."
Moses listened to his father-in-law and did everything he said. He chose capable men from all Israel and made them leaders of the people, officials over thousands, hundreds, fifties and tens. They served as judges for the people at all times. The difficult cases they brought to Moses, but the simple ones they decided themselves.
Then Moses sent his father-in-law on his way, and Jethro returned to his own country.