This sensor is used to detect magnets in the surroundings.
Like the touch sensor which requires direct contact to work, the magnetic sensor works by sensing whether the magnet is near or far away from the sensor.
The difference between the touch sensor is that the magnet can be detected when it’s 5mm apart from the sensor (doesn’t require actual contact).
Rivets of the ROBOTIS DREAM Kit can be used to assemble the sensor onto robots.