A storyboard is a drawn plantation and the base of an animation. In a storyboard, a keyframe is drawn and below some text to describe what is happening. In a good storyboard, the text does not need to be read to understand what is happening, this is because animation is a visual medium and all imagery has to be 100% clear to the audience.
To exemplify this better, on the left we can see an unclear storyboard, without the text it is very hard to understand. Meanwhile, on the right, we have a great storyboard. In this one, you can understand perfectly what is going on and what the actions are on screen without having to read.
