Cubestack (from "Rubiks Cube" and "stack-based") is a stack based esolang which serves absolutely no purpose. The whole language has a total of 56 commands, all of which are moves on a Rubiks Cube. To learn Cubestack see the docs, although I'd recommend against it if you value your sanity.
To use Cubestack, you can either use the online interpreter, download cubestack.zip from the latest release or clone this repository:
git clone https://github.com/tobyck/cubestack.git
cd cubestack/cubestack
node main.js --help