seems some of torrent's common sense you lack. metaphors are eventually limited at explaining. would better taking some time to understand how torrents system is working:
BitTorrent for Beginners: How To Get Started Downloading Torrents
A Beginner's Guide to BitTorrent
at least know this terms' meaning: leeching, seeding, client, torrent file
Can someone explain to me what is reseeding and why is it necessary?
When you have a file(files) and the tracker already has the torrent of this file, you could just reseed this existed torrent instead of creating a new torrent. This is the occasion where reseeding works.Also after I've uploaded a torrent/seeded a file, do I have to keep that file in the same place on my computer? I ask because I reorganize my porn quite often…sometimes I delete old stuff...If I do...does that affect people from downloading the torrents I've uploaded?
you're free to move the file, but once you move it, remember telling the client where the new location is, otherwise the client cannot upload anymore. If you delete the file, you can't upload it obviously until you own this file again. as for whether others can download it after you delete the file, it depends on whether there are other seeders.