If you ever get into animation, you'll find there's two kinds of artists. The top dogs are the keyframers. They might draw a frame with Elmer Fudd pointing his rifle at Bugs Bunny, and another with Bugs's finger in the end, and a final frame where the gun backfires on poor Elmer. That's about two seconds worth of cartoon. Three little frames aren't going to do it.
Someone needs to draw another thirty something frames in between.
The people that draw them are called 'tweeners. The neat thing about timelines is you only mess with key frames. Your brain does all the tweening. I'm looking out over my future, and I like what I see. There I am acing an interview for a great position.