IIS Application Pool contains all web applications on your domains. If your service provider has given you a dedicated IIS application pool, it allows you to have a level of isolation between web applications used by your domains and web applications used by other domain owners that host their web sites on the same server. Because each application pool runs independently, errors in one application pool will not affect the applications running in other application pools.
Once you enable the application pool, all web applications on your domains will be using it.
To stop all applications running in the application pool, click IIS Application Pool on your home page and click Stop.
To start all applications in the application pool, click IIS Application Pool on your home page and click Start.
To restart all applications running in the application pool, click IIS Application Pool on your home page and click Recycle. This can be handy if some applications are known to have memory leaks or become unstable after working for a long time.