The DRV2605 from TI is a fancy little motor driver. Rather than controlling a stepper motor or DC motor, its designed specifically for controlling haptic motors - buzzers and vibration motors. Normally one would just turn those kinds of motors on and off, but this driver has the ability to have various effects when driving a vibe motor. For example, ramping the vibration level up and down, 'click' effects, different buzzer levels, or even having the vibration follow a musical/audio input.