Sharepoint-Farm Account

The Farm Account is the one you typed in when you ran the PSconfig utility when you installed SharePoint. It is the account used to run the Central Admin web site app pool and has dbo access to the configuration database. Because it has higher permissions than other service accounts in the farm it should only be used where SharePoint requires it. For example you can't run User Profile Synchronization without it. You can see more about it here:
http://technet.microsoft.com/en-us/library/cc263445.aspx