The function keys are the two keys located below the screen with information that depends on the context:
On the main screen, the left function key is used to access the Function Menu. With the right function key
you access the Phonebook.
The navigation keys are the five keys of the central selector, four of them located on the edge for movement in the four directions (up, down, right, left) and the center key to accept, OK.
On the main screen, these navigation keys are shortcuts to functions: Music, Sound, Calls, Messages, and Menu. It is possible to configure these shortcuts in Settings.
On the left side, you have two keys to raise or lower the audio volume:
And on the right side, the switch to turn the flashlight on and off: