Photoelectric sensors are devices that detect the presence or absence of objects by using light. They work by emitting a beam of light, usually infrared, and measuring the amount of light that is reflected back. When an object interrupts the beam, the sensor can trigger an action, such as turning on a light or activating a machine. These sensors are commonly used in various applications, including industrial automation, security systems, and automated doors. They are valued for their reliability and ability to work in different environments, making them essential in modern technology for detecting objects without physical contact.