The "casting" of content to a TV really took off with the introduction of the Google Chromecast device. While other devices supported the feature to one degree or another, the popularity of the Chromecast -- and the fact that "casting" is the only way to use the device -- made it more familiar to the end-user.

The most common use of "casting" probably isn't what you think. That is, it doesn't really send the content from the mobile device to your casting device.

App Casting

Commonly, someone would launch an app on a phone or table -- say, Netflix -- and select a video to play. The user would press the "casting" icon on the screen and select the device to play the content.

The content will not actually be sent from your phone or tablet to the device. Rather, the app on the device will launch and play the content. A connection between your mobile device and the casting device will be maintained for the purpose of controlling the playback.

Screen Mirroring

Some people confuse app casting with "screen mirroring." Apple devices use a process called "AirPlay" to accomplish actual screen mirroring. Miracast is another process supported by some Android and Microsoft devices. AirPlay is generally more reliable, but some users have had great success with Miracast.

To mirror your screen, you would use the appropriate command to open the option -- since it's device-specific, not application specific, it would vary from device to device -- and select your mirror device from those found on the network.

The content is actually sent from your device to the TV. Using your casting device, your TV effectively becomes your device screen.

Tab Casting

Another method of casting is also commonly confused with "screen mirroring," too. It's actually tab mirroring or casting. That is, playing of content in a browser tab on your television screen. Most commonly, that's done with a Chrome browser and a Google Chromecast.

It will usually work for any content you can open in a browser tab. It won't work for standard applications. It doesn't turn your TV into a computer monitor, except for content in a browser tab. But, it does that very well.

Casting Devices

Most devices support casting in some way, shape, or form. The most reliable screen mirroring is from an iOS device (iPad, iPhone, etc) or an OS X device (a Mac) to an Apple TV. Tab Casting is best done with a Google Chrome browser (Mac or Windows) to a Chromecast. App Casting is supported on many apps and on most of the devices covered here, including Roku, Chromecast, Fire TV, and TiVo.