A reed switch is an electrical component that consists of two thin metal contacts sealed within a glass tube. When a magnetic field is brought close to the switch, the contacts close, allowing electricity to flow. This makes reed switches useful in various applications, such as in security systems and automotive sensors. Reed switches are known for their reliability and fast response time. They can be activated by small magnets, making them ideal for use in door sensors and proximity switches. Their simple design and low power consumption contribute to their popularity in many electronic devices.