Use of .NET Framework 4 Client Profile

The .NET Framework 4 Client Profile is a subset of the .NET Framework 4 that is created specifically for client applications(including WinForm, WPF, WCF, and ClickOnce). This enables faster deployment experience by having smaller download sizes and quicker install times. An application that targets the .NET Framework 4 Client Profile has a smaller redistribution package that installs the minimum set of client assemblies on the user's computer, without requiring the full version of the .NET Framework 4 to be present.

When you deploy an application that targets the .NET Framework 4 Client Profile, you only need to deploy the .NET Framework 4 Client Profile. If you are deploying using ClickOnce, you can select the .NET Framework 4 Client Profile as the .NET Framework Launch Condition. 

If you deploy the .NET Framework 4 Client Profile and your application targets the .NET Framework 4, the user will be prompted to install the .NET Framework 4 when he or she tries to run your application.
Source: MSDN