6' Monoprice Data Link Cable: 6' USB Type-A to Type-A 2.0 Cable Expired

I think most people are going to buy this without knowing what it is!

I don't know about this particular one and there is no link to a manual but here is how most data link cables work.

It is not a plain USB cable, it is a USB cable with a box in the middle that sets up a peer-peer connection between the two computers plugged in at either end (this is similar to manually setting up a peer-peer connection over a USB cable if the OS allows it but simplifies it for any Mac or PC)

It is not really plug and play, you do need to install software related to it. When plugged in, it mounts a drive that will have the installation program.

There are two main functions:

1. Keyboard and mouse sharing. This is similar but not the same as KVM switches which physically transfer the connection between the two computers. This one allows the keyboard and mouse on one of the connected computers to act as if it is connected to the other with some limitations. You can set it up to move the cursor off the screen of one computer to the other screen (like you had a dual display on the same computer). So you can interact with either screen by moving the mouse over. The keyboard input is sent to the screen that has the mouse currently. This works for entering simple text, etc but there may be serious limitations with control characters. Things like Windows key, alt commands, etc may or may not be transferred. So, it is more limited than a KVM switch. On the other hand, it allows cut and paste text between the two and drag and drop files between the two just like you had a dual display on the same computer which KVMs cannot do. You can disable this function if you prefer.

2. File sharing. As mentioned above you can drag and drop files from one computer to another by using the mouse to drag from one screen to another. Or these things usually come with a file transfer app that allows file copying on the same screen by displaying drives on both machines - like most ftp or scp clients.

From a security perspective, never connect your computer to another that you do not own or not sure of its safety from viruses, malware, etc. This will allow those to spread faster than covid-19!

It's for computer to computer connection if you want to use Microsoft's integrated migration wizard or for keyboard/mouse sharing. You can simply drag and drop files from one PC to the other and the mouse rolls over to the other monitor. Otherwise, you could just use a USB stick to transfer files. I see this coming in handing when transferring big files between PCs when you don't have a large enough USB stick