It's a heat simulator that allows you to investigate conduction, convection and radiation.
The first time I used the simulator in class, I used it to demonstrate convection in fluids.
I placed a hot source at the bottom, and a cold source at the top, and as was to be expected, the air rose above the hot column, and fell below the cold column.
Then I was able to show them that the convection didn't depend on a hot and a cold source, but would also work with just one of either.
The software also comes with a whole load of Examples to play with.
But what was really interesting, was that when I continued playing with the simulator, sometimes my convection examples would split into two cycling air cells, one above and to the left, one below and to the right, with the hot air blasting right for the cold source, rather than rising.
That's really interesting, because I've experienced this when using smoke demonstrations in class, and the fact that the simulator can capture that behavior shows how accurate this teaching tool actually is.