.NET 4.5 is the most advanced version of .NET ever released with Windows Store and Office Store apps.
Microsoft has done a great job putting a detailed document on MSDN. Here is a list of key technologies that are new or updated in .NET 4.5
- .NET for Windows Store Apps
- Portable Class Libraries
- Core New Features and Improvements
- Tools
- Parallel Computing
- Web
- Networking
- Windows Presentation Foundation (WPF)
- Windows Communication Foundation (WCF)
- Windows Workflow Foundation (WF)
You can read complete details here