Battle Rating, or BR for short, is a number that represents the total power and strength of the player's character. It is perhaps the most important part of the game, as all players across the selected server are measured in strength by their BR.
Any upgrade in equipment, skills, Wrathwings, and other activities a player does to overall better improve their Power, also increases their BR. Some upgrades offer greater increases in BR compared to others, however all are important for the growth of a character.
BR also allows players to gauge somewhat accurately if they are able to beat various opponents in PvP settings, and specific PvE settings. The higher a players BR, the stronger that player is, and the more activities they can accomplish with relative ease.
Players can see their overall rank in Battle Rating in comparison to other players on their servers. To do this, locate the button in the lower right hand of the screen, with that sub-menu closed, click the button above it represented by 2 helmets, then proceed by clicking Ranking. Please note, lower level characters will not be able to access this feature right away.