A motion sensor registers movement in a specific area. This is useful, for example, if you only want to switch on certain lamps if there is movement in a certain room inside or outside. In that case, there is no longer a need for a light button. When you place a motion sensor with an outdoor light, you ensure that this light switches on when there is movement. It varies per motion sensor how long the light stays on. The angle at which a sensor detects movement differs per product.