When you create an episode of your podcast on Acast, you'll see a few different options. One of them is the episode type.
This lets you state what kind of episode your listeners should expect, and how the episode will be displayed in Apple Podcasts.
Full (default). This is an ordinary-length (for your show) podcast episode.
Trailer. This is a short, promotional piece of content that represents a preview of your current show.
Bonus. This is extra content for your show (for example, behind-the-scenes information, commentary, or interviews with the cast or cross-promotional content for another show.)
Here's further information from Apple about the podcast tags for your show.
Note: There are hundreds of podcast apps, including Pocket Casts, Castbox and Overcast. Not all podcast apps respect/reflect these different episode "types", so you should bear that in mind when making your choice.