Door sensors are devices designed to detect when a door is opened or closed. They typically consist of two main parts: a magnet and a sensor. When the door is closed, the magnet aligns with the sensor, creating a closed circuit. When the door opens, the magnet moves away, breaking the circuit and triggering an alert. These sensors are commonly used in security systems to monitor entry points in homes and businesses. They can send notifications to smartphones or trigger alarms, helping to enhance safety and provide peace of mind for users.