HDMI switches, like network switches, allow you to connect more HDMI devices to your TV than you can out of the box. If your TV only has two ports but you want to have four gadgets hooked up, you connect a switch to one port on your display, then plug the other units into the switch. It's not great for an HDMI port to constantly have a connector plugged and unplugged; plus, the more often you do this, the higher the chance that you'll pull it out improperly. Switches change inputs through automatic detection, buttons on the unit and/or a remote. Definitely get a model with a remote, since getting up to change the signal every time is no fun.