[ Microsoft's MSDN ] The Summary Tag in C#

(C# Programming Guide)

The <summary> tag should be used to describe a type or a type member. Use <remarks> to add supplemental information to a type description. Use the cref Attribute to enable documentation tools such as Sandcastle to create internal hyperlinks to documentation pages for code elements.

The text for the <summary> tag is the only source of information about the type in IntelliSense, and is also displayed in the Object Browser Window.

Compile with /doc to process documentation comments to a file. To create the final documentation based on the compiler-generated file, you can create a custom tool, or use a tool such as Sandcastle.