HIIT is fast and furious and is all about making you fitter. You can do these workouts in any order and mix & match as you please.
BUILD mixes faster more explosive movements, with some slower more deliberate and focused movements to increase full-body strength. You can do these workouts in any order and mix & match as you please.
The hybrid program (such as SALT 1.0) provide a more structured, macro approach to your training. To get the most out of these programs, these workouts are designed to be completed sequentially.