Stories are a port from Instagram, which is a copy of a Snapchat feature. Basically like "status message" in good ol' IMs, except a) made from pictures or videos, and b) self-destructing after 24 hours.
I personally hate them as a concept, but that's because I generally don't like transient things on the Internet. Given their popularity, however, I'm guessing that more than half of photo sharing activity on social media is through such self-deleting broadcasts, leaving no trace and no ability to catch up on it. Which is probably why the platforms like it - it exploits FOMO to keep you checking the app every day.
I personally hate them as a concept, but that's because I generally don't like transient things on the Internet. Given their popularity, however, I'm guessing that more than half of photo sharing activity on social media is through such self-deleting broadcasts, leaving no trace and no ability to catch up on it. Which is probably why the platforms like it - it exploits FOMO to keep you checking the app every day.