From what I've read DTube works similar to torrents, but a little differently. Videos are stored on users' nodes (computers), not on servers as with YouTube and similar services. Your video is initially only stored on your node until someone else watches it. That's why after you "upload" a video you are presented with a page that tells you to keep it open to seed your video. You're not actually uploading your video, you are uploading the file metadata to the network. Once someone else watches your video it is stored on their node, but only temporarily. If a lot of people watch a video and others continue to watch it, you and other people will have no problem accessing it. If no one watches a video for a while, it will end up being automatically deleted from all nodes and no longer available. You can also pay someone to "pin" your video to their node.