The username/user id is created on the Timios Exchange as your unique identifier. Compared with the address, the username has better legibility and memorability. For example, if A transfers money to B, A will no longer need to copy and paste the complicated address of B,  instead of A just needs to enter the username of B. 

The username is case sensitive. If you transfer to a wrong ByteTrade username, we can do nothing in this situation because every transaction is recorded on blockchain and cannot be replayed. The best solution is to try to find that user in our community and talk to them.