Based on the selected components while doing the installation we will find respective service to each component in the Windows Services. e.g. SQL Server, SQL Server Agent, SQL Analysis Services, SQL Server integration Services etc. There will be a user for each and every service through which each service will run. That use is called Service Account of that service.

Mainly we categorize the Service account as below:

Local User Account: This user account is created in the server where SQL Server is installed; this account does not have access to network resources.

Local Service Account: This is a builtin windows account that is available for configuring services in windows. This account has permissions as same as accounts that are in the users group, thus it has limited access to the resources in the server. 

Local System Account: This is a builtin windows account that is available for configuring services in windows. This is a highly privileged account that has access to all resources in the server with administrator rights.

Network Service Account: This is a builtin windows account that is available for configuring services in windows. This has permissions to access resources in the network under the computer account.

Domain Account: This account is a part of our domain that has access to network resources for which it is intended to have permission. It is always advised to run SQL Server and related services under a domain account with minimum privilege need to run SQL Server and its related services