Electronic speed controllers (ESCs) in the hexacopter
ESCs translate the signal to an electrical supply. On a multirotor, every motor has its own ESC, and each ESC is connected to the flight controller. After computing the inputs, the controller directs each ESC to adjust its speed in order for the craft to fly.
ESC refresh rates vary. For multirotors, given that the balance among multiple motors is critical to the craft's ability to stay airborne, high refresh rates are more important than in many other applications where ESCs are used.
The only other major factor to consider is an ESC's maximum current rating, which must exceed the current draw of each motor. Generally, 30A for medium or large drones and 10 to 12A for small drones should be sufficient.
For my hexacopter, I used 40A ESCs.