To manage SharePoint with multiple servers you need three types of roles/accounts:
|SQL Server service account||SQL Server prompts for this account during SQL Server Setup. This account is used as the service account for the following SQL Server services:|
|Setup user account||The user account that is used to run:|
If you run Windows PowerShell cmdlets that affect a database, this account must be a member of the db_owner fixed database role for the database.
|Server farm account||This account is also referred to as the database access account.|
This account has the following properties:
Start the installation with Setup user account and in SharePoint Configuration Wizard you will specify SQL Server service instance (because it will be on other server inside the farm) and Farm Account access.
Single Server Farm
To manage single server farm, all three roles can be handled by one account. So you need only local account (Setup user account) to do all the installation and configurations.
Start the installation with Setup user account and SharePoint Configuration Wizard will automatically pickup the SQL Server Instance and assign Setup user account as Farm account.
See the single farm installation in here.