How Does Ebay works.

Hi everybody

i have some questions about ebay s mechanics

- how does ebay protect thier buyers
if the seller didnt send the item to the buyer how could they know ?
does the seller gets his money immediately after the buyer send them ?
from where they gets the money for the guaranties if the seller already took the money from them and have 0 dollars on his account
- how do they guaranty that the seller and buyer will not do the exchange process out of ebay so they can avoid fees...

How Does Ebay works.