Arcs. Animators are obsessed with arcs. This is because most organic actions happen along an arched path, giving fluidity and realism to human and animal motions.
Mechanical movements, on the other hand, usually happen along straight paths.
Whether you are animating an organic being or a mechanical device, Blender allows the tracking of motion paths. This is extremely helpful when animating, and can give you answers when you watch the movements you create and feel that "something isn't quite right".
005-Tracking.blend. It has our character Otto with some very basic and unfinished animation of a jump. Let's track the arcs so we can make our animation better.