View In-Between Frame
In-Between Frames are what is created between keyframes, and are the result of the chosen interpolation process. In some cases, the mathematically-generated in-between frames will give the animator the intended results. However, it is far more common for the animator to add polish and finesse to force the in-between frames to convey are far more pleasing, humanistic result. In short: don’t stop with what the computer gives you. “Plus it”, make it better. That’s what Disney did. That’s what Pixar does.