Animator need to create great poses. Part of a great pose is a great silhouette, one that "reads" clearly.
The image on the left is taken from Eric Goldberg's book
"Character Animation Crash Course", (we have a copy in the library), one of the best books on character animation.
Eric shows how a single pose can get an instant "read" from the audience. Even though the images are shown blacked out in silhouette, we still know exactly what the character is thinking and doing.
Always make sure your poses, whether drawn or digital, communicate exactly what the character is thinking, feeling and doing.