Full duplex allows for the communication in both directions at the same time. For instance a signal sent with half duplex would have to wait for the completion of the data transfer in order to transmit a reply. With full duplex a reply could be sent and received at the same instant.
A widely used example of this full duplex system would be a telephone. You can communicate simultaneously with the party on the other end of the phone. You have the ability to speak and be heard at the same time.
This is the very foundation of today’s internet. You can be sending information for example searching for a term on a search engine such as Google and at the same time you can be receiving data in the form of a download in progress from another page on the internet.
Full duplex allows for the non-existence of wasted time. You can be doing multiple things on line at the same time. This is the ultimate of multi-tasking. Take the average user for example. Most users have at least 2 or 3 windows open at a time on their computer. Some of which could be Facebook, a calendar of personal events on their computer, and checking their email. Using full duplex allows a person to be working on multiple tasks at the same time.
Another useful advantage analogy for the full duplex mode would be communications radios like the ones that are used in some restaurants. The person at the register takes the order and is able to communicate with the all of the preparation staff at multiple departments to convey the order requirements.
This helps speed up the order and all staff can work collectively to get the food ready in a more timely manner.