The document discusses different types of transmission media used to transmit data between devices. It defines transmission media as the means through which data is transformed from one place to another. Transmission media are broadly divided into guided media, which provide a physical path for signal propagation, and unguided media, which transmit signals through air. Common guided media include twisted pair cable, coaxial cable, and optical fiber cable. Common unguided media include microwave, infrared, and radio waves.