The difference to YouTube is that it's not intended to create a huge platform centralizing videos from the whole world on a single server farm (which is horribly expensive).
It's based on <a target="_blank" rel="noopener noreferrer" href="https://activitypub.rocks">ActivityPub</a> to connect with tools <a target="_blank" rel="noopener noreferrer" href="https://peertube.cpy.re/videos/watch/da2b08d4-a242-4170-b32a-4ec8cbdca701">like Mastodon</a> for example.
It's based on <a target="_blank" rel="noopener noreferrer" href="https://en.wikipedia.org/wiki/WebRTC">WebRTC</a>, a free and open-source project for web browsers.
PeerTube is developed by <a target="_blank" rel="noopener noreferrer" href="https://framasoft.org">Framasoft</a>, a French non-profit popular educational organization on digital issues.
It employs a developer, <a target="_blank" rel="noopener noreferrer" href="https://github.com/Chocobozzz">Chocobozzz</a>, who works since 2018 on PeerTube projects: