The Web Serial API is a web technology that allows web applications to communicate directly with serial devices, such as microcontrollers and sensors, through a web browser. This API enables developers to read from and write to these devices, making it easier to create interactive applications that can control hardware without needing additional software. By using the Web Serial API, users can connect devices like Arduino boards or Raspberry Pi directly to their web applications. This opens up new possibilities for projects in areas like robotics, IoT (Internet of Things), and data collection, all while maintaining a seamless user experience in the browser.