This type of method redeems vouchers in a single request. You simply call the request to immediately redeem the given voucher code and any other valid vouchers for the same device and app as the given voucher. This is the simplest method of redemption, and should be used when there is a rare chance your server will later fail while attempting to grant the redeemed content to users once the request is complete.
This type of method redeems vouchers in two API calls - the first begins the redemption process and the second one commits it, similar to how a database transaction begin-commit cycle works. Your server is responsible for actually granting the redeemed content to the current user (identified by the device ID) between the two calls, and avoid committing vouchers that it could not grant the user for some reason. This method should be used when there is a reasonable chance of your server failing to grant voucher content to your users.
For more details, see the "Using the TROPHiT Redemption API" in the full reference guide.