Stories = up to 60 seconds, and you can keep adding to it, but fans will have each segment available for only 24 hours, then you can add to Highlight for others to see it anytime in the future. You can also add clickable Link to a Story that you can’t to other video formats.
Reels = Any video that is 15 minutes or shorter is now called a Reel.
Posts = includes Reels, but not Stories. And you can upload a video of up to 60 minutes.
For in-depth discussion about all this, go to my Instagram Course.