This reference article describes what an Application Pool is, and its purpose is to improve the understanding of its use in servers. This knowledge base article can be used by agents of any level. This article serves as an introduction to Application Pool.
Application Pools allows isolate applications from one another, even if they are running on the same server. This way, if there is an error in one app, it won't take down other applications.
Additionally, Application Pool allow you to separate different apps which require different levels of security. An Application Pool can contain one or more applications and will enable you to configure a degree of isolation between different web applications. For example, if you want to isolate all the web applications running in the same computer, you can do this by creating a separate Application Pool for every web application, and place them in their corresponding Application Pool.
Because each Application Pool runs in its worker process, errors in one Application Pool will not affect the applications running in other Application Pool. Deploying applications in Application Pool is a primary advantage of running Internet Information Services (IIS) 6.0 n Process Isolation mode because you can customize the Application Pool to achieve the degree of application isolation that you need.
When you configure Application Pool for maximum availability, you should consider how to set Application Pool for security. For example, you might need to create separate Application Pool for apps that require a high level of protection, while allowing apps that require a lower level of security to share the same Application Pool.