You won't be expected to know all the Redis commands, but you should have a basic idea of how Redis works. Note that the console on the left has hints which you can see when you start to type a command. Check the Redis documentation for a full list of commands.
Any data you insert will disappear when you reload the page. In addition, your connection will be lost if the page sits idle for a long period of time. This is intended to allow you to play with Redis little, nothing more.