Yes it is the firmware that is flashed to the Arduino. According to the blog post on 14Dec2015 by vicious1 (https://www.vicious1.com/marlin-firmware/) he is using the standard Marlin firmware that most DIY 3D printers and CNC machines use. Since not everyone has an Arduino, he pre-loads the marlin firmware on the ones he sells, since you probably wouldn’t buy one from him unless you intend to build a MPCNC. Of course, since you already have several, just flash marlin to any of your compatible arduinos and you will be set as far as that goes, however, you will still need a RAMPS board (or equivalent) to attach to the arduino. The RAMPS simply takes the signals from the arduino and passes them through the stepper motor drivers (essentially translating micro-controller signals into higher current and higher voltage control signals for the stepper motors).