This document discusses different types of transmission media, including guided and unguided media. Guided media provides a conduit for signals and includes twisted-pair cable, coaxial cable, and fiber-optic cable. Unguided media transports electromagnetic waves without a physical conductor, also known as wireless communication, using radio waves, microwaves, and infrared. Wireless channels are subject to more errors than guided media due to interference but use techniques like directional antennas and varying frequencies to mitigate issues.