A set-top box (often abbreviated as STB) is a consumer electronics device that connects a television with an external signal.
As countries around the globe make the switch to digital TV, consumers with older analogue TVs can opt to purchase a high definition (HD) set-top box as an inexpensive way to upgrade to digital TV.
Most STBs offer additional features including an electronic program guide, parental locks and digital signal improvement. Some also offer internet connectivity, digital video recording and playback from hard drive (also referred to as a personal video recorder or PVR), access to numerous apps, and video on demand services.
The Verge recently put together a comprehensive STB buyers' guide which explains what to look for when purchasing a set-top box.