Earn a guaranteed certain amount of money (typically anywhere from $0–$680) when you sign up to be an Uber driver and complete a certain number of trips (typically between 30 to 100) within a certain number of days of signing up (typically 90).
The referral amount and the minimum trip requirements vary from city to city and change frequently.
The referral amount is not a bonus. Rather, if the amount you earn by completing the minimum trip requirements is less than the referral amount that was guaranteed when you signed up, Uber will pay you the difference.
The referrer will receive a certain reward amount if the person referred completes the minimum trip requirements in the designated amount of time.