Namespace or Assembly?

Question

I am getting very confused between Namespaces and Assemblies. Are System.Data and System.Web Namespaces or Assemblies?

I have noticed these

Answer 1

The file that you see in GAC is System.Data.dll that is an assembly and that contains namespaces including System.Data. If you view the Reference properties in Visual studio then you will see:

Later if you right click on the reference and select view in object browser you will see namespaces in that particular assembly.