Be extremely careful, most sellers in the GPU/Computer hardware section are fake or scams. See philipma's post :
https://bitcointalk.org/index.php?topic=2907919.0If you are interested in learning more about escrows and how they work you can do so here :
https://bitcointalk.org/index.php?topic=133931.0Within that thread there is also a link to all the active, trusted escrows that everyone on the forum uses when they are serious about a transaction.
Escrow List :
https://bitcointalk.org/index.php?topic=2439910.0Escrows act as a middle-man, a trusted and unbiased party that only has the interest in making sure the deal goes down without a scam taking place, making sure both parties are satisfied. You can set terms depending on your particular trade, but essentially escrows help ensure security and a smooth trade by holding both parties to their end of the deal.
For example, if you were to use an escrow when you wanted to exchange your
BTC to Ethereum with another user, then you would have a few options; User 1 sends their funds to the escrow, once escrow confirms they have the funds the 2nd user sends their funds directly to User 1 and once that transaction can be confirmed the escrow will release funds to the User 2. Something like that.