They control two different things:

• Focus mode = how the camera focuses.

  • AF-S: focuses once when you half-press, then locks.
  • AF-C: keeps adjusting focus while you hold the button.
  • AF-A: camera chooses between AF-S and AF-C.
  • MF: you focus manually.

• AF-area mode = where the camera looks for focus.

  • Single-point: uses the selected point.
  • Dynamic-area: starts with your selected point, but uses nearby points if the subject moves.
  • Auto-area: camera chooses the focus point.
  • 3D-tracking: camera tries to follow the selected subject.

So, for example, AF-C + Dynamic-area means the camera continuously focuses and can use nearby points to keep a moving subject in focus. AF-S + Single-point means it focuses once using one selected point.

They are complementary, not duplicates: one sets focusing behavior, the other sets focus-point selection/tracking behavior.

If a camera had AF-area options but no separate Focus mode, then the focus behavior would likely be fixed, simplified, or handled automatically by the camera.