From everdrivestore.com, “What is an Everdrive?”:

An Everdrive is a flash cartridge that allows you to play games on your console. The cartridge is easy to use. You “drag and drop” files from your computer onto a * micro SD card that you insert into the Everdrive. When you turn on your console, a list of games will appear. With your controller, you select the title, and you’re done!