According to Exodus 18, Moses appointed officials over groups of 1,000, 100, 50, and 10.
The arrangement followed advice from Jethro, Moses's father-in-law, who observed that Moses was spending all day judging disputes among the people. Jethro recommended that Moses teach the laws, represent the people before God, and delegate routine cases to capable, trustworthy officials.
The officials were organized into tiers, allowing them to handle ordinary disputes while bringing only difficult cases to Moses. Exodus says they were to be men who feared God, were trustworthy, and rejected dishonest gain. This made the system both administrative and moral.
The passage is sometimes summarized as Moses appointing judges, but the text uses several related descriptions for the delegated leaders. The answer officials is the broad term matching the hierarchy described in the chapter.