The dual coffee maker has one side for K cups, and one side for the basket where you put the ground coffee. The machines come with a reusable metal basket so theoretically you shouldn't need to bring filters - but I still do as I don't like to take the chance someone hasn't damaged or stolen the reusable basket - they are the standard flat-bottom small type filters (not cone style). I bring my own coffee mostly because I like fresh-ground beans, but they do supply ground coffee bags if needed.
The water reservoir gets filled and feeds both the k-cup and pot brew sides - you choose with the buttons on top which one you want to use. Because the pot-side only has choices to make 6, 8, or 10 cups, if you wanted to brew a smaller pot of 2-4 cups, I'd advise just filling the reservoir with the amount of water you need, and choosing the 6-cup option - it will just brew until it runs out of water, so you can make less than 6 cups.
The k-cup single-serve side has no heating element, while the pot side does have a heating burner pad to keep the coffee in the carafe hot.