Stands for "Keyboard, Video, and Mouse switch." As the name implies, a KVM switch allows you to used multiple computers with the same keyboard, video display, and mouse. Now, most of us don't need to use two computers at once. In fact, using one computer at a time can sometimes be a challenge. However, there are situations where using a single keyboard, mouse, and display with multiple machines can be very practical.
For example, software programmers may use a KVM switch to alternate between two or more computers with different operating systems. This allows them to test their software on multiple platforms when developing a crossplatform application. Network administrators often use KVM switches to monitor and control multiple servers at a time. These KVM switches may support eight or more computers at once. By simply pressing a button on the KVM switch, the administrator can view the display of any machine connected to the switch and control it with a single keyboard and mouse.
Of course, KVM switches can also be used by the everyday home user. Some people may find it useful to have two computers at their desk, such as a home and work computer, or a Mac and a PC. In these situations, a KVM switch can accommodate both machines, allowing them to share the same monitor, keyboard, and mouse. Because only one of each is needed, the result is far less clutter on the desk. This leaves room for stacks of papers, mail, and other objects to clutter up the rest of the desk.
Since most keyboards and mice use a USB connection, most KVM switches include USB ports. Older models may include PS/2 or serial ports. The connection for the monitor may be a VGA or DVI port, or both. If you plan on using a KVM switch for your computer setup, make sure the ports match the display and input devices you are going to use with it.