There are three types of context-sensitive help:

1. Whole topic is shown when you point to some member in source code or Object Browser and press F1.
2. Quick summary is shown in IntelliSense and Object Browser.
3. Short property description is shown in Properties Window.

F1 Context help

To see Visual Studio dynamic help integration including context-sensitive help, go to the code editor and select expression with some method, property or other documented member. If you press F1, the proper topic should appear.

You can also press F1 on a member in Object Browser to invoke the help topic.

IntelliSense and Object Browser Quick Info

If you create a project with reference to your DLL and you use methods or properties from that DLL, IntelliSense in Visual Studio automatically shows their description and description of parameters as you write them. Description of a method or a property is taken from their <summary> tag in comments.

You can see the summary information in Object Browser as well.

Property Description in Properties Window

When you select any property of a control or a component in Properties Window, you can see a short description.

This description is not extracted from your comments but from Description attribute of your property. So if you wish to display this info you need to define Description attribute:

[System.ComponentModel.Description("Indicates button state.")]
public bool Pushed

VSdocman offers an easy way to do it through context menu.