The Arduino UNO is the "original" Arduino board, designed to make it easy to learn about electronics and computing. It's based on the Atmel ATmega 328/P microcontroller running at 16MHz.
"Arduino" really refers to the pin connections on the board, so you can have Arduinos based around other microcontrollers. ArdEx will only work properly with a 16MHz ATmega328/P based board. Get an UNO or a clone at Amazon, eBay or AliExpress. Google search.
NOTE: Genuine Arduinos work straight away with Windows, Mac or Linux. Cheap clones appear to need a driver installed manually before USB communications are recognised. If you're not sure about installing drivers, it might be best to stick to a genuine Arduino (or use Linux).