The main difference between a neuromodulator (such as Botox) and a filler is their mechanism of action. Neuromodulators, like Botox, work by temporarily relaxing or paralyzing muscles. They are used to treat dynamic wrinkles caused by muscle movement. Fillers, on the other hand, are substances injected into the skin to add volume, fill in wrinkles, and enhance facial contours. They are often used to address static wrinkles and age-related volume loss.