Explanation of terms:
Set Top Box: This refers to any additional device designed to receive a digital signal and convert it so it can be viewed on a TV (or Video/DVDR) that would otherwise be unable to use it .
Terrestrial TV: This is a TV signal broadcast from a land-based mast - usually the same mast that transmitted the old analogue signals (as opposed to satellites).
Satellite dish: is the dish-shaped device required to pick-up signals from a satellite. Because of the distances involved (around 22,000 miles above Earth) the TV signal is very weak. A dish is aimed directly at the satellite and the signal is reflected into the focal point of the dish. The precise positioning of the dish is therefore critical, and a few degrees out and there will be no signal received. Also when there is exceptionally bad weather, the raindrops can overwhelm it and the picture will freeze or drop-out.
The satellite itself is in geostationary orbit, which means it is travelling around the Earth's equator at precisely the same speed as the Earth is turning - thus it appears to remain stationary at a fixed point in the sky. TV signals destined for a particular location (such as the UK) may come from more than one sattelite but - to all intents and purposes -they will be located at the same point in the sky.
A satellite's "footprint" is the geographical area in which the satellite can be easily seen and detected. This is why, in the UK, we cannot pick-up signals from the USA for example.
Cable TV: This is TV down a wire or fibre-optic cable (usually the same wire as a "Cable" telephone and/or Broadband service). This is not the same as a British Telecom telephone wire. The suppliers of these services busily dug-up roads throughout Britain in the ‘80s to provide this service, but stopped-short of connecting all rural areas. If you are unfamiliar with the term it is probably not available where you live.
Broadband: This is the name given to a digital data service available on a standard telephone line (or a "Cable TV" system) which can provide substantially more, and faster, information for computers than a plain old telephone wire. Without it an e-mail might take 30 seconds to download—with it, it might take 1-or-2 seconds. Of course, quality and speed are roughly proportional to the extra cost involved. A telephone service is also incorporated into Broadband.
High Definition: HD TV is a much-higher resolution TV picture than Standard Definition. In other words, the picture is much sharper than normal.
16:9 and 4:3 (Aspect Ratio): The old TV pictures were broadcast in a rectangular shape with the ratio of 4 wide by 3 high (such as 12 inches wide by 9 inches high). In recent years Europe has adopted a "widescreen" ratio of 16 wide by 9 high. Although most programmes are now made in this format, old programmes were made in 4:3. The solution adopted for this are varied, but include having a black band at each side of the old picture (to cover the extra "4", above) or to zoom-in so the picture fills the width of the screen - this means that the top and bottom of the original picture falls-off the screen and is not seen (not good when there are subtitles or captions at the bottom of the screen). Other variations involve distorting the picture to fit - squashing the top and bottom of the picture. This has the effect of making people on TV short and fat (!) and is particularly noticable on circular and square graphics (they become oval and rectangular). Many TVs have options to control how they respond to the changes in picture ratio, but due to the complex nature of the switching information transmitted, the TV is sometimes not sure what ratio it should be in!
Note: Although old cinema films were in Cinemascope (much wider than 16:9) the TV companies' copies were usually converted into the ratio of the time (4:3) - so if you watch "The Big Country", you will still not see the sides!
