When a SQL services runs on "System account or Local system account" it means it has full access to the entire system resource on the computer which it is running. The Local System account is a powerful account that has full access to the computer. The actual name of the account is NT AUTHORITY\System. The Local System account is powerful only to the machine which it is running however it does not have any rights to access the network. It however represent itself as a computer when it access the network.
This account has minimum privileges on the local computer and presents anonymous credentials on the network. the actual name of this account is NT AUTHORITY\LocalService
This account has minimum privileges on the local computer and acts as the computer on the network. The actual name of the account is NT AUTHORITY\NetworkService, and it does not have a password that an administrator needs to manage.
For enterprise user, It is a best practice to have a dedicated Active directory account/NT account for SQL server services. The purpose of this is that SQL server may need to access several resources on the local computer and on the network. For example you may need to do a backup on a SAN or Shared Drive. You will need a Domain account for the service to do this. The NT domain account must not be owned by any employees on the enterprise because if that employee resigned you will have no access to the network resources and your services will not work.
Although you can manage the SQL services by running the windows service (services.msc) mmc plugin You can administer it much easily with the the SQL Server Configuration Manager shown below. You can run it from the windows start as shown or you can type "SQLServerManager11.msc" from the command line.
Figure 2. The SQL Server Configuration Manager
Richard Mueller edited Revision 28. Comment: Fixed case of header lines, cleaned up HTML
FZB edited Revision 29. Comment: formating