You don't really need to understand TRS, but if you clicked the link, I'll pretend you are interested. Warning: There may be math.
TRS (Tennis Rating System - aka Todd's Rating System) is a conceptually simple rating system that can be easily interpreted for comparing players.
It starts at 0 for players who have no tennis skill and do not seem to pick the game up easily. Picture someone swinging and missing the ball completely more often than not and almost no ability to get a serve in play.
There isn't an official upper end because it's never been used to rate people above 45, but I think the theoretical cap for Serena and Rafa is about 65 to 70. Comparisons to other rating systems are below.
What does a rating mean? It mostly means things when compared to another player. Each point on the system represents a one break of serve margin of victory over someone else (or a 2-game edge). So, if a player rated 35 plays against a 32, the expected result is a 3-break victory - about 6-4, 6-2.
So, every 6 points on the scale represents an expected 6-0, 6-0 victory.
For a frame of reference, using descriptions that are fairly true for Oregon Girls Tennis:
Most of the better varsity teams in Oregon have 1-2 players rated 31-35.
The middle of their varsity team is rated about 22 and their lower varsity members are rated 12-15. That is a very wide range. Some schools without very deep varsity teams have players rated around 9 or 10 in their lowest positions.
State champions in Oregon tend to be rated 42-46.
Division III college players range from 29 up to about 42.
Division 1 college players range from 40 up to about 55.
Every high school team is different. The top teams in the league I coach in tend to be "flatter" than other leagues. There are not many players over 28, but their lower players are rated closer to 16.
TRS 28 is about equal to the 3.5 / 4.0 NTRP border, which I think tends to be a UTR of 5 (I love the concept of UTR but it is horrible at differentiating players below ratings of 6, especially women).
TRS 22 is about equal to the 3.0 / 3.5 NTRP border