Chef - difference between knife.rb and solo.rb

Question

When I run chef-solo without specifying the -c solo.rb parameter, it throws a warning

[2015-06-25T14:53:04-04:00] WARN: *****************************************
[2015-06-25T14:53:04-04:00] WARN: Did not find config file: /etc/chef/solo.rb, using command line options.
[2015-06-25T14:53:04-04:00] WARN: *****************************************

Presumably it's looking for a system solo.rb file because I didn't specify one explicitly.

I also have a .chef/knife.rb file available.

1. What's the difference between the solo.rb and knife.rb files? They seem to have the exact same info defined - cookbook_path, file_cache_path, log_level, etc.. - so it seems redundant
2. Does chef-solo ever look for and use my knife.rb file? It's looking all over the place for a solo.rb file, and was wondering if it ever falls back to searching the default .chef/knife.rb file.

Thanks!