When you click "Login with Battle.net" button, you will be redirected to Battle.net website where you will be asked to authorize our application to access your basic profile information (BattleTag, WoW characters list).
After you authorize our application, Battle.net will redirect you back to our website along with an authorization code.
Our server will then exchange this authorization code for an access token from Battle.net API.
This access token is then used to fetch your profile information and WoW characters list from Battle.net API.
We only store your Battle.net ID and BattleTag in our database to identify your account. We do not store your password or any sensitive information.