It also helps to do a little reading about the terminology. When I first signed up for a trader account online I felt I needed a degree just to understand how to use it.
You get used to it though, and that's why these sort of demos can be very useful. I'll try and compile a list of different types, though, as some are more useful than others, plus some allow you to experiment in different market sectors or focus on one, ie, equities, forex, commodities, etc.