What's the difference between pre-advertising and post-advertising?

Pre-screening advertisement: it is to play video advertisements within a specified time before all the films in the designated cinema. Film patch advertisement: refers to the advertisement that copies the enterprise product advertisement or enterprise image advertisement with the film and plays it before the film is shown. Also known as follow-up advertising. The previous concept is a comprehensive statement of Baidu Encyclopedia. Translated, all the advertisements played before the movie are called pre-screening advertisements. However, patch advertisements, including corporate promotional videos or corporate image advertisements, are broadcast before the film is broadcast. The scope is smaller. It can be said that the pre-screening advertisement of the film includes the advertisement of the film patch.