BitTorrent has some flaws, but what p2p app doesn't?
I was exposed to trackers and seeds and .torrent files and all sorts of oddities while trying to figure out how to get what I wanted.
A tracker is a service (web, app) provided by a server to categorize and keep track of the seeds that people are offering, the number of current downloads, and meta-data of that variety.
A seed is a file-for-offering. The first time a specific file is made available via the server, a hash is made. When people complete a download of the file, a checksum is run against the original seed's hash to validate the download.
To download a file, you'll need its .torrent - which is a pointer back to the BitTorrent server which brokers a connection with users who have what you need. As you download the file, you're also uploading the same file to others as brokered by the server. This is the first problem I encountered.
I don't mind sharing, but the issue is that the download turns into a pyramid scheme. There's a broad base of users who have some of the file, but only a few users who have all of it. Therefore, the beginning of your download is pretty snappy - but the more you download, the fewer the sources you can download from and the slower your download goes.
For a whole day and a half I was stuck at 94.8% of my file download waiting for someone to come online who had the last 5.2% of the file. Such aggravation!
The next drawback is that you just can't be sure of the validity of the file you're downloading. Just because the checksum against the original seed passes, doesn't mean you'll have downloaded any meaningful data. This isn't a BitTorrent-specific problem, but it's one I encountered when the installation disc I burned from the .dmg I downloaded didn't pass its internal validation process - which, luckily for me, was a skippable step of the installation.
What have I learned? Depending on what you want, it may be difficult to find trackers. Once you've found the right tracker, you still can't be sure you're getting what you want.
P2P user: "I also like to live dangerously."