As defined in Internet Information Services (IIS) an application Pool is a collection of one or more URLs that are serviced by one or a set of worker processes. After installation of SharePoint, open IIS Manager. You will notice application pools in iis.
application-pool
Accounts used by application pools or service identities are in the local machine Administrators group SharePoint
Rule Name: Accounts used by application pools or service identities are in the local machine Administrators group. Summary: A user account that is used by application pools or services must have permissions of a domain user account and must not… Read More ›