What is 'symbol' and its uses?

Hello,

I am confused by the meaning of 'symbol' as found in 'man global'. In
particular, the output from 'global -c' and 'global -cs'.

How should they differ? I am using GNU global with a java project but I
am new to Java.

Also, does 'global -r TAGNAME' include definitions in the results? If so
can I exclude them?

Thanks,
Leo