A serial is like a novel, except broken up into tiny pieces that gets read and critiqued by an audience constantly peering over your shoulder. They're wondering if this is supposed to be a plot hole, or if something makes any sense, and you have to feed them enough interesting material each time. Also, serials can be longer.
It's the difference between a movie and a TV show. A movie is a small, self-contained chunk. They're entertaining, you can get excited about them, but it's shortlived and fairly static. They only give you a short amount of time to make the characters into real people. TV shows become part of your schedule, something you get to look forward too, with characters that can change with the times and fill out a lot more than what their cumulative twenty minutes of the movie would show. There's a little bit of back and forth between creator and audience, too.
Nice to meet you, nursingcapsarecool. I'm Psycho Gecko, of the serial World Domination in Retrospect. To keep up the TV show metaphor, I'm like pro wrestling, or the stuff on Spike TV.
Unfortunately, I never settle on a theme song for long, so it's probably best to go for one that's purely informative in the meantime: https://www.youtube.com/watch?v=Lk_dRzaBoUM