[CMake] Basic Tutorial Help

[Adam A Smith]

I feel that these are stupid questions, but I'm still a little confused 
about the basic example.

It mentions 3 source files:  hello.cxx, demo.cxx, and demo_b.cxx.  So is 
hello.cxx supposed to be the source file for a library, with no main()? 
That would possibly make demo.cxx the entry point for the executable, but 
then what's demo_b.cxx?

Another question--why are the directories called ./Hello and ./Demo? 
Why isn't there a ./Bin?

Sorry--I've been working in Java for years, and I'm only just getting back 
to C++ after a long absence.

Thanks,
Adam