The Microsoft Web Farm Framework enables you to easily define a “Server Farm” that you can add any number of servers into.  Servers participating in the “Server Farm” will then be automatically updated, provisioned and managed by the Web Farm Framework. 

What this means is that you can install IIS (including modules like UrlRewrite, Media Services, etc), ASP.NET, and custom SSL certificates once on a primary server – and then the Web Farm Framework will automatically replicate and provision the exact same configuration across all of the other web servers in the farm (no manual or additional steps required). 

You can then create and configure an IIS Application Pool and a new Site and Application once on a primary server – and the Web Farm Framework will automatically replicate and provision the settings to all of the other web servers in the farm.  You can then copy/deploy an ASP.NET application once on the primary server – and the Web Farm Framework will automatically replicate and provision the changes to all of the web servers in the farm (no manual or additional steps required).

The Web Farm Framework eliminates the need to manually install/manage things across a cluster of machines.  It handles all of the provisioning and deployment for you in a completely automated way.