As the narrator points out, running Ubuntu on your phone would theoretically allow you to do lots of cool things that aren’t possible with most existing smartphones. Chief among them is powering an entire desktop PC setup — minus the actual PC — with your phone by connecting it to a monitor and other peripheral devices.
The video also suggests that as an operating system designed for general purpose computing, Ubuntu is better positioned than Android or iOS to meet the needs of people who who want to use their phones to get real work done, not just send texts or make calls — although Ubuntu will be able to do that too, we’re promised.