Trade-in is a term in which you can sell your old and used devices and there will be no need to go to any retail store for doing the same as this feature is available in Verizon. You can exchange your old electronics with Verizon by providing them the gadget information and you will get the estimated value of the trade-in which is the cost your device will be sold for. And after you approve it, you will be sent the kits in which you can ship your item to be sold and within one or two billing cycles, you will get your credits.