Chassé is a classical ballet term meaning “to chase.” When a dancer is doing a chassé, they have one foot extended forward, the back foot then “chases” and meets up with the front for a quick moment before the front foot shoots forward again, all while traveling forward. They are often done one after the other in a series, but not always. The step is called chassé because the back foot literally looks like it is chasing after the front. All variations are triple-step patterns of gliding character in a "step-together-step" pattern.
In color guard, you never know which direction you will be moving, so we have two exercises for chassé, one moving forward and the other one moving sideways.