What Are Breakdown Drawings in 2D Animation?
Other users have already briefly outlined the situation and if you are curious about what is 2d animation then it is better to start with the basics and terminology. The creation process itself is not as complicated as it might seem, but you should study the basic tools and their names, then it will be easier for you with the tutorials and if you want to take some courses.
In traditional animation a breakdown is the pose between two other main or key poses. The breakdown poses are secondary ones and these are used to describe motion, rotation, elbow bending, timing eases. Thus a smoother effect in animation is achieved. Usually the breakdown keys adjust automatically following the keys before them. Such effect is found in mostly all animations and an example can be explanimations Donker Media. In cut-out animation, breakdown is the effect of creating a puppet with articulation by breaking the character into small pieces. Whether the breakdown is used in traditional or cut-out animation the effects are completely different.