An escrow is service that allows safer payment by securely holding a buyer's coins in escrow(
hold) until the terms of the sale are met and as a result the buyer releases payment to the seller.
In short you can say Escrow is a temporary hold on the money/bitcoins until both parties Agree that one of the party have got the shipment or Goods correctly , after the confirmation of first party he triggers the person(Escrow) holding money/Bitcoin to release it to the second party.
The escrow may charge fee as much as 1% or above his wish and as per his agreement.
Graphical representation of Escrow Service:trusted escrow List over This Forum:
https://bitcointalk.org/index.php?topic=855778.0