Thanks for the suggestion, carboncareful, anyone else think this would be a good idea?
A topic is a category (like 'Food') that you can start a discussion in. A discussion (also sometimes called a 'thread') is the list of comments you can add your comment to (like the one we're in now, called 'forums & topics'). 'Forums' is a general word for all the discussion pages: topics, discussions, active conversations etc.
Hope that clears things up a bit - all this terminology can floor the best of us! Don't worry too much though, we're sure you'll be able to make yourself understood whichever words you use!