B-Movies - are the lesser known types, which most of the time go straight to video, and may have a cult following. They don't make as much, but usually they're crazy enough to be very entertaining. Low budgets lead to silly props, bad acting and plot holes which will probably leave you very confused.
ex: Night of the Living Dead, Attack of the Giant Leeches, Pretty much anything with a zombie in it

C-Movies! - to be honest, I just made up. These consist of no-budget movies that I, or others make, just because they can. Note this is not an indie catagory, since they seem to have larger production values, make a little more sense than b-movies and are most of the the time about friendship, discovery and a journey. So, we'll just skip that.
ex: GOSHZILLA!, DuctWars, Six-Aces

Series - are weekly shows split up along the course of a season. It may also include TV specials and made for TV movies, but those may go up above, I don't know.
ex: Strangers with Candy, Get a Life, SNL

Note: Movies don't alway fall into those three clear cut catagories. Something like Bats or From Dusk til Dawn is well filmed, has known actors/actresses and a fair budget, but the plot and execution is so silly, that you can't put them on the same level as a George Lucas movie. Then again, The Blair Witch Project was shot on 16mm and had three unknowns, but still made it to the theaters and became a huge success. I'm not sure why I just put a disclaimer for this section, it's seems like a really dumb issue.