Storyboards are visual organizers, typically a series of illustrations displayed in sequence for the purpose of previsualizing a video, web-based training, or interactive media sequence. Sometimes they are also used to previsualize a web site or application, although typically in that case wireframes are used as part of an iterative design process.
Simply put, animatic is an animated storyboard. Boards are brought together in an editing program and are cut together with the correct timing and pace of the film. They include basic sound effects and dialogue recordings.
Similar to storyboards, animatics are used for pre-visualizing the film before production starts. Animatics are extremely important for making an animated movie, since they let you see what the movie might look like for the first time. This is when you first get a sense of the pacing, the rhythm and the progression of your film.
This is also the last step before going into 3D, so it’s important to make sure that no more story changes need to be made.