I'm from 2012

magnet is just the most important parts of a .torrent file, short enough that it can be represented by string of letters. this doesn't require as much web hosting space as a .torrent, and magnets can be, for example found in a google cache entry if the server goes down as it's just text.

the torrent client starts off with that small amount of info and tries to get the rest of the metadata (i.e. the contents of the full torrent file) then continues as normal.

idk about not being able to select individual files, I use qbittorrent and I can do that

Magnet is a reference to a magnet link.
Basically, without telling you stuff you could just look up on your own:
You can't select the files in the torrent before it starts because the list of actual files in the torrent and the blocks/pieces that make up those individual files are stored in the torrent file, which if you're using magnet links, you don't have immediately.
A magnet link is basically a link to the information which would be stored in the torrent files you're more familiar with. I use Transmission, so I can tell you that all you have to do is wait for the metadata to finish downloading, then you can select the files you do and don't want in your torrent.

>>192885
see
>>687343
or
>>>/g/sqt
or
>>>/g/oogle

>>192887

Ah ok thank you. I found where to select the files, but for some reason it won't let me un-check the boxes for the .sfv, .m3u and .nfo files. I realize they're small and don't take up any space, but I still don't want them usually. Any way to do that?

Also I realize I could've Googled magnet links, but I would've sifted through paragraph after paragraph figuring them out and wasting time. The quick, simple explanations I received here are much appreciated.

>>192889
With Transmission, and using magnet links instead of torrent files: by the time you open the file selection window after Transmission has downloaded the torrent's metadata from peers, it has also already downloaded the text files since they are so small. They therefore appear in grey with a percentage of 100% in the file selection window, and are no longer deselectable.

As the other anons have explained, a magnet link is a string storing the most important thing about a torrent: its hash, a long hexadecimal ID:

magnet:?xt=urn:btih:<hash>

It can store a few other things such as the torrent's name or the URL of some trackers:

magnet:?xt=urn:btih:<hash>&dn=<name>&tr=<tracker-1>&tr=<tracker-2>&...

The torrent's file list cannot be stored in the magnet link, but it is stored in the torrent file.

It's enough to give a BitTorrent client a torrent's hash: the client will find the rest of the torrent's metadata (e.g. the file list) and then start downloading the data.

You can see the torrent's hash at the beginning of a torrent file if you hexdump it on the command line.

>>192889
>Ah ok thank you. I found where to select the files, but for some reason it won't let me un-check the boxes for the .sfv, .m3u and .nfo files. I realize they're small and don't take up any space, but I still don't want them usually. Any way to do that?
No.

Bittorrent works over blocks, not files. All the files are crammed together one after the other, then the whole lot is split into blocks. Bittorrent can only verify complete blocks, and can't seed unverified blocks, so it has to either download the whole block, or not download the block at all.

So if you're downloading the last mp3, and its last block also contains the entirety of the .sfv, .m3u and .nfo files, then you can't verify the last block without also downloading the .sfv, .m3u and .nfo files, which means you can't download that mp3 without also downloading the .sfv, .m3u and .nfo files.

Some torrents get around this by adding padding files that are all zeroes between each interesting file so no interesting file shares a block with any other. Because they're all zeroes, most OSes can store them without taking up any space, and because undownloaded files start off filled with zeroes, if you delete them then verify the torrent, the torrent client will recreate them with their exact contents by magic.