Before I started writing I had never heard of a novella. I had to look it up. They’re roughly 10k-15k words, so they’re around a fifth of a short novel. They aren’t short stories. Short stories are capped at around 5k. When I was first trying to publish stories, I found absolutely no outlets for novellas. Either they didn’t exist or they were so well hidden that I never found them.
Now they’re all the rage. Brian McClellan wrote piles of them for his Powder Mage series. Matt Wallace has some standalone novellas coming out on Tor soon. Kevin Hearne, Delilah Dawson, and Chuck Wendig are smashing three novellas together into and selling it in one delicious piece. And yeah, I have mine out now, too.