I’ve been running my PeerTube instance for more than a year now so hopefully I can help :
if you only watch, it doesn’t use your device for storage, only some of your bandwidth if P2P is enabled. If you want to host content, e.g a video of yourself explaining how to design your own smart speaker using only FOSS, then you should setup a server which will need storage for your videos.
Happy to clarify more if you need. Overall you can watch content from video.benetou.fr and most likely all bandwidth will come from my server. You can not upload your videos there though (unless if I accept making an account for you, which I won’t). There are other servers though, public ones, which allow registration and where you can thus upload your content too.