You see that little white weight scale underneath my green bars? well if you click that and add reputation then it gets complied in ones reputation points. the accumulation of these reputation points adds up and as it reaches certain numbers - 300, 400, 1000, and with that you get to a certain portion of green bars.
I for instance have 1417 reputation points, and i suppose that is why I have 10 green bars.
The bars just represent the amount of rep points you have received.
Last but not least, you get the green bars by posting valuable sh1t. this is because other members will read it and like what they read and will give you reputation.
But honestly who cares. They are just egoistical bars of narcissistic supply. Dont worry about them. Worry about bettering your REAL life
