Before creation, an animated(and often live action) film goes through a process of being drawn out into storyboards. Many different versions of the film are created during this process, until the artists feel they have a story that works.
The storyboards are put into a film format to make sure everything is flowing and cutting well, and that is referred to as an animatic.
Dia de los Muertos went through many many versions before the team felt is was ready to go into production. This was the final animatic that the team created as a guide for creating the film.