Firstly, I must correct your n00bness, and introduce you to the three P's... (Actually, your not a n00b your a newbie. You show some willingness to learn
noobs are the tards that give newbs a bad name.)
The Three P's:
Planetside is not about EXP.
Planetside is not about EXP.
Planetside is not about EXP.
Right, once you have shifted from the "must get exp mentality" you may actually begin to enjoy the game, and play it how it was designed to be played.
In answer to your question, a "zerg" is a term meaning a massive group of aimless sheep whose wishy washy goal is to overpower and conquer the enemy with sheer weight of numbers.
In principle this may seem a good idea. . . But most people "riding the zerg" have no order, they are a chaotic bunch of , for want of a better word, n00bs.
No direction other than "go with teh flow". . Respawn, shoot, die, rinse repeat...
Generally a major zerg has no benefit to your empire, as the squads participating in the zerg would be better off channeling their efforts onto other bases and towers AWAY from the zerg, but co-ordinate there attacks, this would result in a far more effective use of the available resources and man power.
100 people standing around for 15 minutes because "they just cant leave the SOI cos I wont get meh gay exp" is lame, and a true sign of an ass bandit.