Teamrating
* Visible.
* Required for rewards.
* Reset when a new team is created or at the beginning of a new season.
* Not used for matchmaking.
* Primarily represents the team's standing relative to other teams.
* Moves towards the Matchmaker Rating over time. The larger the discrepancy, the faster the Team Rating will move.
* Looks like a new team will start with a rating of 0 from now on, rather than starting at 1500. This makes Arena less depressing for a below-average team, and allows Blizzard to stratify gear even in the below-average zone. For example, if a piece of gear requires 1300 rating, a low-ranked team can work to achieve that rating, rather than simply restarting the team or playing very few games in order to minimize rating loss.
Personal Rating
* Visible.
* Required for rewards.
* Reset at the beginning of a new season.
* Not used for matchmaking.
* Is primarily a control on Team Rating, trying to prevent players from leeching off a high-ranked team.
Match making Rating
* Only shown after an arena has ended.
* Not required for rewards.
* Does not reset.
* Used to match teams against each other.