What is Programmatic in its various variations explain in simple language intelligibly and clearly?

Question

contextual advertising

In addition to the fact that this is an automation of the purchase of advertising.
What is the difference between online/offline/mobile/social Programmatic?

Answer 1

In simple terms: mass automatic purchase of advertising on sites. Large advertising networks sell ads on the basis of a real-time auction (search in RTB search engines), whoever pays the most - the audience dances. Advertising is purchased according to the criteria ...
It used to be like ... You go to the site, negotiate, buy, show the audience you need, pay ...
Now everything is centralized and automated.
This is in general terms and highly exaggerated.