Videotex (better known as Viewdata in the UK) began as a service provided by the German post office. Using low-cost computer terminals and modems users could access post office computers to view data assembled by registered 'information providers'. These information providers paid a subscription to the post office and, in turn, could charge the end user a fee for viewing each 'page' of information they had provided. In practice, of course, most information providers (such as national airlines providing flight information) did not charge the end user for data thus displayed.

The standards developed in Germany were taken by several other countries and modified for use in their own, similar, services - the most well known in the UK being the Prestel service originally provided by British Telecom. Over the years those differing versions were largely brought back together but principal services from France, Britain, Canada and America still varied in some respects.

A basic videotex terminal is not unlike other computer terminals in appearance with a separate keyboard and screen - the keyboard is fairly standard but the screens do tend to be smaller than usual. Normally the screen is only capable of displaying 40 columns of text (although 80 columns is sometimes now available) which means that the characters are large and easy to read. Simple 'mosaic' graphics are available which, although only slightly better than 'block' graphics (where individual character positions can be completely blocked-in to form shapes), can be quite effective when combined with the use of the 8 colours available.