One of the features of the S8200 and T2200 units is the ability to cast videos and audio from a server such as Plex (which can be set up on a compute, or another service) or from a tablet, smartphone or laptop. 

It saves you from using a USB and going back and forth with cables which can save time! It also means you only need to plug in the unit to the TV and nothing else. This guide will help you with 

Casting from the T2200 or S8200

Casting from a PC 

Casting from a Mac

Casting from a Tablet / Smartphone