[quote=DragonBeastMode]
I have a quick question what do this thing mean?[Please, don't let this get after 300. This is designed to be something hard to raise. For every 100 you unlock a tier and get a perk point, which you can spend in sub-tiers for new abilities. Class Mastery advances as you use abilities. I will inform you every time you reach the next 100. Perk points can also be obtained from events and other things of the like.]
[/quote]

Basicly You can ignore it, but don't go crazy, The highest player (James Sic. me) has 469 ish, and he runs a guild and has been at it since day 1 and is level 80. 
its class level in short.