It seems when I'm delving into the branches of the module tree, I can
find most modules either in the neighbour modules variable, or in the
defined names variable.

The first is polluted also with names of thing that's not contained
modules, but mere dependencies, and the second is polluted with the
names of classes local to the module.

Stranger still, modules I create myself, or existing modules after
unloading and reloading, no longer appear in defined names, but just in
neighbour modules. 

What does it all mean?

Daniel