By binding your account, you create types of login methods of your choice, which essentially enables you to play on multiple devices.
The first time you start playing Heroes Quest, one guest account is created. As long as you play on the same device, you will always be logged in to your account. After you bind your account with one of the login methods, the connection between your device and your account will be revoked.
To log in with your account on other devices, you need to go into the game, click your avatar -> options -> accounts -> log off. Then choose the login type with which you have linked your account.
Currently the game support login with Facebook and custom email-password combination.