What's US Postal Service Priority Mail and Standard Flat Rate Shipping?

What's the difference on Ebay of US Postal Service Priority Mail and Standard Flat Rate Shipping?What's US Postal Service Priority Mail and Standard Flat Rate Shipping?
Priority is usually 2-3 days delivery time, Standard a little longer. Ebay has nothing to do with it.What's US Postal Service Priority Mail and Standard Flat Rate Shipping?
If a listing says Standard Flat Rate, it could mean anything, it covers the seller so he can decide what to charge and how to ship after the auction ends, unless you ask before you bid how much it will cost to your location and by what class of service he will ship.