A service account is simply an account that is used as the security context that Windows uses to run a service. Each SQL Server service needs to be configured with a service account, which is granted the appropriate permissions to run the service. This chapter discusses the general considerations for service accounts. You then examine how service accounts can be exploited. Finally, I discuss the appropriate service account strategy.
Service Account Types
SQL Server 2016 supports the following types of account as service accounts:
Local user
Domain user
Built-in accounts
Managed service accounts ...