In 1936, Alan Turing published a paper about a hypothetical machine for performing computations that came to be known as a "Turing machine". The deterministic variant is the foundation of modern computers. Some guy decided to build a "classic" Turing machine that mimics the machine described in Turing's 1936 paper. So now you can watch a Turing machine on your Turing machine:
Theoreticians will note that the machine has almost all the elements of a "classic" Turing machine: a read/write head, a tape with symbols (the computer "program", if you will), and the ability to move said tape forward and backward. It does not have the infinitely long tape described by Turing, but, well, that's impossible.