Proximity sensor is a tool to detect the presence of objects or people. The sensor can detect existence of the object that approaching through signal sent without physical contact called proximity sensor. As i said earlier that the sensor uses signals to detect objects, it is called an electromagnetic field where the field signal changes. Objects can be perceived and referred to as proximity sensor targets. Distances that can be detected by sensors are the nominal time range. There are also sensors that can be adjusted to the nominal range or means that can provide information of distances of objects detected. The proximity sensor can be a mainstay and has a high enough resistance because there is no mechanical part of the physical contact between sensors and objects are aligned.
I will set an example
Android is used by all people who have touchscreen sensor to activate touch that deliberate. The most common skanario in everyday life is the ears that come into contact with the screen, when you make a call.
Robot when moving by sending a signal through the sensor received by the robot, eg the robot moves toward the target then the sensor will send a signal and the robot will vibrate when touching something that exists.
http://ams.com/var/plain_site/storage/images/applications/industrial/industrial-robotics/1035514-1-eng-GB/Industrial-Robotics_f615.png
image source: http://ams.com
https://engineeringinsider.org/wp-content/uploads/2018/01/sens-note-feb-2010-a.jpg
image source: https://engineeringinsider.org
https://2.bp.blogspot.com/--I7BrrXyrHE/WBzEGAGXGUI/AAAAAAAAB18/XHyoI4r9yM0KIDVNk2uuj5H5a6TIwSUdQCLcB/s640/proximity-sensor.PNG
image source: .androidon.top