UDP (User Datagram Protocol) is a communication protocol used to send data over the internet quickly and with minimal overhead. Unlike TCP, UDP does not establish a connection or check if data packets arrive intact or in order. This makes UDP faster and more efficient for real-time applications like video streaming or online gaming, but less reliable since lost or corrupted data is not automatically resent. Its simplicity also makes it susceptible to misuse, such as in denial-of-service attacks where large volumes of data can be sent rapidly.