How do I buy a gun online?
Buying a firearm online is a bit of a misnomer; you can't directly purchase a firearm as you can other products. The process is you would place an order from a seller (be it an auction site, retail site or out of state seller). Once the order has been paid the seller will need to ship the gun to a FFL (Federal Firearms Licensee) in the same state as you, normally a dealer willing to perform the transfer and local to you. When the gun is received you will be notified and can set an appointment to actually go through the transfer.
What is a transfer?
A transfer is how the ATF describes the process during which the gun is transferred out of the hands of the dealer and into your posession.