Relays work sort of like a subreddit. You can share a link to your videos on any free Nostr relay, but you will need to host your videos on another service. If you are already uploading to another provider, like YouTube, you can share those links for free.

Relays don't store content like videos. We are transmitting JSON to share videos from anywhere else online. So, your videos will be to be hosted "somewhere" which can be anywhere.