What are the three power modes and what is each one used for?

The three power modes are Eco, Auto/Med, and Boost. Eco mode provides maximum run time for longer cleans, Auto/Med mode offers the optimum balance of power and run time with suction that automatically adapts to dust levels when a cleaner head is attached, and Boost mode is designed for intensive spot cleaning of ground-in dirt. You can change power modes quickly using a single button. (Page 3)