I've no personal experience with a seedbox, but:
Seedboxes can download a torrent's files (the data files / movies) when you add the torrent to it's torrent client. While they do that, they already upload back the parts they got to others and generate usually a share ratio above 1 due to their heigh bandwidth. (and make the life for non-seedbox users difficult).
You get a download link for the .torrent file (the torrent) in our torrent list, which unlike the button works without java script.
Some members have automated the downloading of torrents to their seedbox by the RSS feed. A member has made a tutorial in the "Guides" section of our Forum.