While GIFs may be mostly familiar to you from your Twitter feed, they are a surprisingly good  way to make animated screenshots for quick how-to's and issue reports. Oftentimes they work even better than video, because they are lightweight and will be automatically played in your email or Slack message. Plus, you can use them in tutorial articles like this one without adding too much weight to the page.
Apple hasn't embraced GIFs yet, although with emoji in the Touch Bar already being a thing, you might as well expect a GIF maker in the next macOS update. For now, however, you're going to need a third-party tool for animated screen capture.