This is all of the views your video got, added up. Doesn't matter where people watched it, or how long they watched it for. If they watched it, it counts as a view. Someone put your video in an email? That's a view. Someone shared your video on twitter, then someone watched the video through the tweet? That's a view.

For a lot of people, this stat is considered the ultimate stat. At the end of the day, most testing / thumbnail changes / title changes, are with the goal of getting more views. Everything else is just a stepping stone. Keep this in mind - if you raise other stats, but views aren't going up, you probably want to change something.

Because this is "All Views", it includes things like External Views, which are views from twitter/etc. This means that you can get a bunch of views on twitter, and this number will be high, but the youtube algorithm isn't necessarily pushing your video.

Larger creators usually focus on Browse and Suggested views, as most other view counts are usually small in comparison.