This is slightly off topic, but can someone explain this to me. I'm looking at the Google Fiance page for FB: https://www.google.com/finance?q=NASDAQ%3AFB http

This is slightly off topic, but can someone explain this to me. I'm looking at the Google Fiance page for FB: https://www.google.com/finance?q=NASDAQ%3AFB https://www.google.com/finance?q=NASDAQ%3AFB There I can see that the price is indeed up, but this is "pre-market": Pre-market: 31.10 +4.59 (17.31%) Jul 25, 5:29AM EDT Can someone explain to me how this pre-market works in the background? Is is an summation of an actual work queue of orders that are waiting to be placed once the market opens? I'm really interested how this works from the general technical perspective.