SharePoint 2013 - Administration Accounts

Multiple Server Farm

To manage SharePoint with multiple servers you need three types of roles/accounts:

Account	Purpose
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: MSSQLSERVER SQLSERVERAGENT If you are not using the default instance, these services will be shown as: MSSQL<InstanceName> SQLAgent<InstanceName>
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. Setup on each server computer SharePoint Products Configuration Wizard The Psconfig command-line tool The Stsadm command-line tool This account needs local admin access on the machine to run the SharePoint Setup.
Server farm account	This account is also referred to as the database access account. This account has the following properties: It's the application pool identity for the SharePoint Central Administration website. It's the process account for the Windows SharePoint Services Timer service. This does not have to be the local account.

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.

Ref: http://technet.microsoft.com/en-us/library/cc263445.aspx