Units, appearance, workout vibration, and how diagnostic reports are handled.
Four short sections: Units (pounds or kilograms), Appearance (light/dark/system theme), Workout feedback (phone vibration during a workout — hidden on desktop, which has no motor to buzz), and Privacy (whether a crash or data-loss report sends itself automatically).
Diagnostic reports contain workout activity and error details — never your password or sign-in tokens. Turning the switch off stops future reports and discards any that are waiting to send; it never affects your training data.
Related: "Bodyweight log", "Settings".