When you download a torrent, you’re downloading it from someone else’s computer. That ‘someone else’ is usually an individual, not some file sharing site with redundant servers.
When you download a torrent, someone had to send it. It’s a small cost for individual torrents, but they had to pay for energy, internet connection, hard drives etc. If more people seed the torrent, you get a small bit of it from each seed, spreading the burden.
If no-one with the torrent has their computer on and seeding it, you cannot download the file, because there is no-one to download it from. If there are several seeds with the torrent, then you can still download it even if one or more seeds turn the computer off at night, delete the file, or are overloaded.
You don’t normally need to specify that the sides are parallel if you specify four right angles.