Magnetic cables are normal cable with the ends cut off. Here is an affiliate link to the exact model of magnetic cable that I use.
The tip that plugs into your device is separate from the rest of the cable. The cable snaps on to the cable magnetically, so you can unplug your device without having to worry about it damaging the port on the device.
This is perfect for devices like keyboards, especially if its a device like the Uni v2 where the port is a micro-usb on a pro micro.
You leave the little tip inside the device and snap the cable on and off without damaging the port.
Verdict: Get them. Buy it here.