This is a cable with 2 Type A connectors (the common large flat connector). You plug one end into one computer, the other end into another computer. There is a processor and some flash memory in the cable itself, so when you plug it in, it launches a non-install application (that is, it runs from the cable and does NOT install anything on your computers). The application shows a split window, with a File Explorer-like interface in the top and bottom. Top shows one computer, bottom shows the other.
Drag and drop stuff back and forth between the computers. Simple! Easy! Fast! And a LOT less hassle than going back and forth with a USB Flash Drive (especially if you have a Large quantity of data to transfer, or if you are updating and moving files a lot.)
I use this at client sites - many clients don't want non-company computers plugged into their networks, and even when they permit it, then establishing a connection to another computer (as opposed to simply getting to the internet) is a problem. This cable makes moving projects from my work computer to client system a snap! Great device! Goes in my computer bag as a permanent addition!
Directions say it works PC-PC, PC-MAC and MAC-MAC. I have only used it PC-PC so far, so I can't vouch for the other arrangements, but I have no reason to think they would not work just as well.