Do not even bother with transferring. It was to trade to the second player, however the second player cannot save their character. So if you happen to transfer a rare you found with the intention of reclaiming for use later, it will be lost.
The second player doesn't get the benefit of achievements earned nor save of progress. It would have been nice to transfer items to your other classes by this means. What good is it to find a legendary weapon for the warrior when you're playing as the rogue?