A Slingbox is a TV streaming device that enables consumers to remotely view their cable, satellite, or personal video recorder (PVR) programming from an Internet-enabled computer with a broadband Internet connection. It is produced by Sling Media, Inc of San Mateo, California.

How the Slingbox works

The Slingbox can redirect up to four live TV streams from a cable box, satellite receiver, or PVR to the viewer's PC located anywhere in the home or, when using a broadband Internet connection, anywhere in the world. For copyright reasons, only one user can access the signal from a Slingbox at a time. This way of accessing content is known as placeshifting.

The Slingbox connects a standard-definition TV source (via coaxial cable, S-video, or composite cabling) to an existing Internet connection. Personal video recorders and cable or satellite set top boxes can be controlled through a separate infrared (IR) cable that lets users change channels from the remote location. Software on a user's PC connects to the Slingbox and provides the user interface for viewing the video stream and changing channels.

(from Wikipedia.org)