LIST

If you're in a shop type LIST and it will bring up something similar to above.

If you'd like to BUY something type 'buy <keyword>' so if you're like to buy a plate of fish'n'chips type 'buy plate'.

If you'd like to sell something in your INVENTORY type 'sell <item>'. If they're interested, they'll buy it!

For more information check out: HELP LIST in game.