Takt time (from the German Takt, a beat) is available production time divided by customer demand over that period. It is the rhythm at which you must complete a unit to exactly meet demand — no more, no less.
Takt is the reference point for line balancing, standard work, and staffing. It is set by the customer and is distinct from cycle time (how fast you actually run); the goal is cycle time at or just under takt.