This is a web-based interpreter for the Velo programming language.
Technically, it is velo.lua (an implementation
of Velo in Lua) running under Fengari
(an implementation of the Lua VM in Javascript)
running in an HTML5 document.
Instructions:
Select an example program from the dropdown box and click "Run" to run it. You can also edit the program before running it. Or you could clear the textbox and write an entirely new program there and run it.
You might also want to read the description of the Velo programming language.