The Windows Azure Pack is a collection of Windows Azure technologies available to Microsoft customers at no additional cost. Once installed in your datacenter, the Windows Azure Pack integrates with System Center and Windows Server to help provide a self-service portal for managing services such as websites, Virtual Machines, and Service Bus; a portal for administrators to manage resource clouds; scalable web hosting; and more.

If you want to learn more about Windows Azure Pack (WAP) where do you need to start? The best place to start is the Microsoft Technet wiki page for WAP

And to make it even easier I would suggest you to watch the 1:14 minutes video Building Cloud Services with Windows Server 2012 R2, Microsoft System Center 2012 R2 and the Windows Azure Pack recorded during TechEd Europe 2013.

It has some great demos about Azure Consistent Experiences, Virtual Machines, VM Clouds Administration,Automation (SMA), Usage Metering and Service Reporting.

After watching this video you should be able to understand more about WAP and related concepts like Service Management Automation.

The Windows Azure Pack is free if you have licenses for System Center and Windows Server.