What is the purpose of XSD files?

Question

Since we can query on the XML file from C# (.NET), why do we need an XSD file? I know it is metadata file of particular XML file. We can specify the relationships in XSD, b

Answer 1

You mention C# in your question so it may help to think of as XSD as serving a similar role to a C# interface.

It defines what the XML should 'look like' in a similar way that an interface defines what a class should implement.