Also vibrate for calls
The Also vibrate for calls setting configures whether the phone will vibrate in response to incoming phone calls in addition to sounding a ring tone.
This setting is not intended as a device-wide control for enabling or disabling vibration, but applies only in the specific case that your phone ringtone is enabled (that is, you are not in Silent or Vibrate mode), and you receive a phone call.
When you phone is in Vibrate mode then vibration is always enabled for incoming calls.
In addition, some apps may vibrate your phone as part of the app itself, such as in a game, or as part of notifications that app creates. The control over this is managed by the app, so if you want to be able to disable vibrations in a particular app, you would need to do so within that app's settings.
Note that Vibration can also be disabled in special cases such as when Battery saver is enabled.
Some devices may allow you to choose the strength of vibration from weak to strong.