Introduction to IIS Architectures

The features described in this article were introduced in IIS 7.0 and later. They include the Windows Process Activation Service (WAS) and the World Wide Web Publishing Service (WWW service) The WWW Service manages the following main areas: Web server management, monitoring, and configuration management. The WAS service is now split between two services: WWW service and a new service, called the W3SVC. WAS is a Web server engine that can be customized by adding or removing modules.”]

Source: https://docs.microsoft.com/en-us/iis/get-started/introduction-to-iis/introduction-to-iis-architecture