Check out this video that fully details what Universal Tennis is:
What is a UTR Rating? Why should I have one?
UTR Rating is a number that provides a real and accurate measurement of skill level. A player’s UTR Rating is a number between 1.00 and 16.50. One match result is all it takes to receive a projected UTR Rating. After approximately five matches, the rating becomes fully reliable. As matches are played and entered into the system, a player’s UTR Rating will increase or decrease over time to reflect their current skill level.