This is not an official mechanic, which is at HouseRulesOnTaint.

Everyone has an internal essence pool, that replenishes at a rate set by the mana level.  Unless you are special (an Adept or a Born Mage), you can only use this essence for implanting or powering Cyberware or Artifacts which work through Blood Magic: you don't have the training to move your Essence around voluntarily, so have to do it by moving your blood, which symbolically contains your Essence.

Mundanes have a Personal Essence pool of 7 x Essence + Willpower.  Their Essence is locked at 1.  Born Mages have a mundane Personal Essence pool, and a Peripheral Essence pool of 2 x Essence + 2 x Willpower + 2 x (Sum of Virtues).  Their Essence is locked at 2.  Adepts have Peripheral pools of 3 x Essence + Willpower and Personal pools of 7 x Essence + Willpower + Sum of Virtues.  Their Essence starts at 2 and goes up.

That gives the average mundane a pool of 10, though strong-willed people can get as high as 17.  Born Mages start around 20+34, and could in theory go as high as 24+62=86.  Apprentice Adepts start at 29+12, full Adepts are about 48/20, and in theory an Adept could get up to 72+28=100.

See ExaltedHackingTaint for the effects of using your Peripheral pool.

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Exalted Lunars get a personal pool of E+2W and a peripheral pool of 4E+2W+max(V)*4.  Since we swapped that for Solars, doing the same thing here would give a starting Lunar-based Adept pools of 38/12, where a starting Solar-based Adept has 28/11.  A more advanced Lunar would have pools of 52/20, while an equivalent Solar has pools of 52/20.  Hunh.  

I always figured Lunars were supposed to have smaller pools... they're actually larger at many points, but more dependant on Willpower and that one Virtue.  You very quickly max out at 60 Essence from Will 10 Virtue 5, and after that are only gaining 5 from Essence, whereas Solars have several virtues to increase and get 10 motes per Essence dot.