Television broadcasters show short "outlooks" or "summaries" of the upcoming program, often right after the advertisement (w/ or w/o the Digital on-screen graphic).
What's the term for this short announcments?
I am not aware of any particular term for showing the schedule. It's just a schedule of upcoming programs and may include playing teasers or previews, which are the video clips to promote upcoming shows. It could also be referred to as filler since it is content that is run while the credits are going (which they have to display) but want to fill it with some more interesting content.
You may be referring to a "teaser" or "pre-cap". These are clips of upcoming shows designed to pique your interest and remind you of an upcoming episode.
An ordinary teaser usually runs separately from the program, where (what we always called) pre-caps are teasers that run at or near the closing credits for an episode -- as in "Next time on XXX..."
If that's not what you're referring to, I don't know what term you mean.