you download a program from last fm, when you play music in one of a few players, the program transmits that data to lastfm so that people can see the music to which you're listening
No shit.
Basically, whenever you first download last.fm and sync your iPod after installation, it's supposed to automatically ask you if you want to scrobble tracks from your iPod, since iTunes does that function automatically when you sync anyways. But, since iTunes is one of the worst music programs ever to grace the Internet, it fucked up. So I had to reinstall both iTunes and last.fm, being careful to import my library, since iTunes puts up a lot of duplicate tracks when it scans for songs. I finally got it to work, but after syncing my iPod so much, I could only sync one track since the fucking bullshit that is iTunes didn't trigger the last.fm program like the plugin was supposed to do.
tl;dr iTunes sucks, the plugin from last.fm sucks for iTunes, and iPod scrobbling sucks. Fuck.