Amazon.com pre-orders

[djluis2k6]

I've often gone through Amazon.com for movies I can't find in stores anymore, but I'm wondering this. How does Amazon.com handle their pre-orders? Do they not ship out until their actual release date, or do they ship them out so that they're delivered the day of their release so that you have it the same day it's out in stores? I've heard of people getting their pre-orders early, and some even getting them the day of or before their release dates, so just wanting to verify if this is how amazon.com works on their pre-orders.