A quick guide to Battlenet handles
Each account on Battlenet has a handle associated with it, which is a unique sequence of digits that identifies you on your server. Map makers can acquire your handle via triggers, and will often use it to verify the validity of your bank file's contents. To discover your handle, first navigate to Documents\Starcraft II. Inside that folder, locate the shortcut to your character. It will have the form Name.###@X, where ### is your friend code (may also be 4 digits long) and X is the server ID: 1 = NA, 2 = EU, 3 = KR/TW, etc...
Double click on the shortcut to your character, and then notice the name of the folder to which it takes you.
This outlined number sequence above is the unique Battlenet handle for your character.