Magnet links are just a link which contain meta-data. Example of magnet link: magnet:?xt=urn:btih:c12fe1c06bba254a9dc9f519b335aa7c1367a88a&dnPirate-bay and many popular torrent website have stopped serving torrent file and switched to magnet links.
Instead, you have to use magnet link which has all the information related to files which you are trying to download. Magnet links work same as a.torrent file, but now you cannot download torrent file from popular torrent website. Magnet links have been introduced to replace torrent files, to reduce web-hosting server space and also to prevent any legal issue.