Transmission Medium:

A transmission medium is a material or device that is used to transmit data, sound, or other forms of information from one location to another. 

There are two main types of transmission media: guided and unguided.

Guided transmission media refers to communication channels that rely on a physical connection or guide to transmit data.

 Examples of guided transmission media include twisted pair cables, coaxial cables, and fiber optic cables. These types of media are used in wired communication technologies, such as Ethernet and broadband internet.

Unguided transmission media refers to communication channels that do not rely on a physical connection or guide to transmit data. 

Examples of unguided transmission media include radio waves, microwaves, and infrared waves. These types of media are used in wireless communication technologies, such as cellular phones, Wi-Fi, and satellite communication systems.

The choice of transmission medium depends on the specific requirements of the communication system, such as the distance to be covered, the data rate, and the amount of interference or noise present in the environment.