You can set any monitor in dual display (you obviously need another monitor to call it a dual display), it's independent from the monitor itself and it has all to do with your Pc and graphic card capabilities, modern graphic cards even the low tiers ones have at least 2 outputs that you could fit to the monitors of your choice, even if not identical, and run them smoothly, depending on the use of the dual display more powerful graphic card could fit a gaming dual display set up.
On the other hand you can DUAL display on your monitor which support 2x HDMI inputs and you can switch between two input sources ( two computers for example or a computer and an XBox) and toggle between the two using your monitor " input" menu botton.