What do I need, to run multiple monitors, on a computer?

The easiest way to setup Multiple Monitors, on a computer, is to purchase
a Multi-Monitor ready computer. You can add additional video cards to your
existing system, although this is not recommended, for a novice. You will
need to know many things, for choosing the right video card. You will need
to make sure that the video card is compatible, with your PC motherboard,
Operating System, and Monitor Input Type. A more safe and  easy way to
Add an extra monitor to your PC, is to use a USB to VGA Monitor Adapter.

The monitors used for Multi-Monitor can be different types (LCD or CRT)
and sizes. The operating system manages the monitors' video resolutions,
independently. Video output on a computer is generated by a video card and
is interpreted and displayed by a variety of devices. Video cards are typically
connected to a monitor (of either the CRT or LCD type), however they are
increasingly being connected to projection equipment or television sets. As
a result of this trend, manufacturers have produced video cards which can
connect to several types of display devices using the appropriate interface.
A video card that has two sockets on it (for two monitor cables) is referred to
as Dual Head. Two separate video cards are just as acceptable, and so is
using the motherboard video socket plus a second video card.