The DZ68BC motherboard does indeed have graphic output ports on the motherboard, three of them in fact - DVI-I, HDMI and Displayport. You can find a picture of the ports on page 12 of the DZ68BC Product Guide, available at http://downloadmirror.intel.com/20248/eng/DZ68BC_ProductGuide02.pdf. I'd recommend the Product Guide, it offers a wealth of detail.
To activate these graphic output ports you need to use a CPU chip that has integrated graphics. The i7-2600K does have the necessary integrated graphics, so you are in business. However if you are a gamer interested in state of the art high performance graphics you would do better to use a graphics card.
So there you have it. For normal usage the onboard graphics is fine. For high performance gaming, get a dedicated card.