The first goal of API writers obviously is to deliver a binary with the desired library functionality. But without decent documentation, it’s often of little use for the consumers of it. No matter how good the naming of types and public members is, additional information on the intended behavior, caveats, and so on is invaluable, too.
To stimulate this practice and provide a structured approach for dealing with it, the C# specification defines the concept of documentation comments. They’re only defined meaningfully when applied to user-defined types or members, where the compiler knows how to export them into a documentation file.
Documentation comments are based on XML to structure the different parts of documentation ...