You can use a cable to connect your computer to an HD TV but there are now wireless options as well. If you already have a WiFi network at home you can use an Apple TV or Google Chromecast to wirelessly display your computer’s screen on your TV. These options cost more than using cables but allow you the freedom to work wirelessly.
Apple TV is not actually a TV but a small box that connects to your TV with an HDMI cable. It’s a digital media receiver that does much more that let you put your computer screen on the TV wirelessly. Apple TV connects to Apple computers running Mac OS X Mavericks or Mountain Lion without any additional software. On Windows computers you will need to use an App like AirParrot which will allow you to mirror you desktop or extend it as another computer screen
HDMI - High-Definition Multimedia Interface. For the technical details follow this link to Wikipedia. Newer computers may have HDMI out or you can upgrade your computer with a new video card that has HDMI.