Pool mining is very different to Solo Mining. It's where you work together with other miners combining your hashing power and increasing the chance to solve a block. Once a block is solved, you then share the rewards with other miners and the pool takes it's fee.
So Solo mining is just what it sounds like, mining away on your own, you are rewarded with all the rewards if you solve a block, however you need to have a lot of hashing power and luck much like winning the lottery.
Pool mining is the recommended option for most miners, as you will generally make a steady income from mining in a pool.
Depending on your pool you might have payment settings, here are the two common methods and what they mean.
Pay Per Last N Shares is what PPLNS stands for.This method of calculating payouts includes a “luck” factor. Using PPLNS your payout per share will have a large range(30% more or less on your payouts), but on average, PPLNS earns more than PPS (by 5% or so) in the long run (a month or more).
PPS is also known as Pay Per Share. It is a more direct method where you get a standard payout rate for each share completed.This method eliminates the “luck” in your payout, but can decrease your total income per share by around 5%.Using PPS you get a set number of cryptocoins per share of work you have solved. It has no luck involved so the payouts do not fluctuate.