Tags vs. symbols

Hello,

I have some questions concerning global. Maybe I have missed some things 
in the documentation.

1) Is there some reference as to what is a "tag" and what a "symbol" is 
in the context of global and C++?

2) In a large collection of C++-sources distributed over a lot of 
subdirs, which are based on the principle of one header and one source 
file per class, there are some class names, which I get as a tag, and 
some class names, which I get as a symbol. Has this behaviour been observed?

3) Are class scope and namespaces honoured in global?

Thanks for hints!

Kay