Minitel was designed and deployed by France Telecom (since then rebranded as Orange), then a monopoly telco, with pilot deployments starting in 1980. The initial idea was to provide an electronic phone book that would replace the paper white and yellow pages that were delivered every year to each phone subscriber: once you got a Minitel on a free loan, like my parents did, you no longer received the paper phone books.

The modem was based on the V.23 standard, which nobody else to my knowledge used anywhere else: 1200 bps download and only 75 bps upload. Yes, the Minitel was designed as a top down, read-only system, in a typical big telco vision.

Instead of the traditional ASCII character set, the Minitel used a semi-graphic symbols set following the Videotex standard. This allowed the Minitel to not only display text with accented characters, but also some relatively crude graphics (no HD at the time).

The real breakthrough happened with the "Kiosque" services, accessed through a premium number (generally 3615, which quickly became part of the French pop culture): the revenues were shared between France Telecom and the service operator, a profitable business model for both. Through the kiosque system, you could access a bunch of services, like booking a train or plane ticket, ordering items from the traditional French mail order catalog companies like La Redoute: My mom was already doing eCommmerce back in the mid-1980s; to her, this was faster than sending her order by mail.

As usual with new technologies, the most profitable side of the business had to do with sex: plenty of adult oriented bulletin boards, messaging, dating, etc... This was quite a flourishing business throughout the 1990s when the Internet eventually took over.

Paradoxically, the wide scale presence of the Minitel system in France may have slowed down the initial uptake of Internet access for residential users. Initially, the technocrats and French pols viewed the Internet with a lot of suspicion: an American invention with no identifiable revenue stream. Although well present at universities, research labs  and businesses, it was difficult and costly for an individual to get Internet access at home, until about the turn of the century. The newly appointed telco regulator started enforcing a policy of strong competition: plenty of ISPs appeared on the scene in the early aughts, most of them now gone or "consolidated" into the four main telcos now active on the French market.