What are the "thumbs up (and down)" icons for?

CdK explains it .here ...

OK, so we can vote on every topic and every post, and this raises it or lowers it in the listings by common opinion.

Does the number indicate how many votes it has received, or perhaps the net result of the votes (e.g. three Plus votes and one Minus vote =2)?

Why is the Thumbs Up icon green on some threads/posts and just grey in others?

Thanks,
Tom

the number indicates the net voting result.
if it reaches a certain negative threshold (i forget the exact number... 6 maybe?), it is automatically collapsed.

green thumbs indicate threads/posts you've voted up.
your posts automatically get a green thumb.
grey thumbs are other's threads/posts awaiting your verdict...

Thank you!

You can choose not to have other people's thread or post collapsing not affect you at all. Got to Your Preferences, and make a choice regarding 'thread filter' and 'post filter'.