"Classifieds" is a general term for buying/selling/trading in newspapers and on the internet.
He means, we should have a section where...hmm, i'll give an example.
I make a topic called "Selling old Nokia 6233"
And in the topic I say how much I wanna sell it for, give a total price including shipping, give details, post pics of it, etc.
People might post saying "How about I pay $90 instead of $100 for it + i'll pay for postage and handling?!"
etc etc...
Not really needed to be honest, but I suppose it could be implimented.