Kilometer per hour is a measure of speed, typically used in countries that use the metric system. In these countries, road speed limits are calculated in kilometers per hour, which is abbreviated as kph or km/h. As its name implies, this unit represents the distance (in kilometers) traveled by an object for one hour. This measure is usually an average, that is, if a car traveled the distance of 210 km between two cities and to take this route, it took an hour and a half, so we will get a speed of 140 kilometers per hour (140 km/h). This does not obviously mean that the car has constantly shifted at this speed, there may be parts of the route on which it has been faster and parts where it has circulated more slowly.
The Knot is a unit of measure of speed, which has a direct correspondence with the nautical miles per hour, which in turn are related to the curvature of the Earth. It should be noted that since the knot is a measure of speed, one should not say knot per hour, since in this case (when measuring velocity versus time) we would be talking about acceleration rather than velocity. This unit is usually used for sea and air transportation. In the past, one of the most common ways of estimating a ship's speed was to launch from the stern of the boat a float connected by a cable that had knots made at regular distances. That said, as the boat moved away from the float, we counted the number of knots that were dropped during a certain time, measured at that time by the emptying of an hourglass.