Whats the yellow gauge arount the portrait?

[hazbahal]

I was wondering what is the yellow gauge arount the portrait? It fills up after each kill, and keeps going this way...

What is it? What it stands for?

I really have no clue...

[Alhanthir]

Its the xp meter, when the gauge fills one of the little circles get filled, that means you gained 10% of the experience needed to achieve the next level, when you do that 10 times, you level up.

You can see exactly how far you are from the next level in the character window.