What is it:
The .NET Framework 4 Client Profile is a subset of the .NET Framework 4 that is optimized for client applications. It provides functionality for most client applications, including Windows Presentation Foundation (WPF), Windows Forms, Windows Communication Foundation (WCF), and ClickOnce features.
This enables faster deployment and a smaller install package for applications that target the .NET Framework 4 Client Profile.
.NET Framework Client Profile: