This is an extra USB power cord for the Electric Eel Wheel Nano.
You can use this with any USB power bank or with a USB wall plug charger. This page explains how it works in more detail.
This is the same USB cable that ships with every EEW Nano 1.1 so you don’t need it if you order that version, but the standard version of the EEW Nano 1.0 did not come with this cable which is why it is sold separately.
This does not work with the EEW 6.0. In general you can’t power the EEW 6.0 from a USB power port because it does not provide enough power for that larger eSpinner.