Yeah bit ad is short for advertisement.

Advertisements have always been something to make you buy something you wouldn’t otherwise think of buying. Okay yeah a preview for content that’s on the same platform can be like an ad, or a type of ad, but I’ve already paid for the streamijg service so it’s not really trying to get me to spend extra money on something else.

As for FBI warnings and producer logos (besides displaying the logo of whomever made the thing you’re already watching), what are they advertising?