Interesting question for a Dane, very iteresting indeed. I don't find it stupid to ask, only not to ask :)
We click our tongue ('slår smæld med tungen') when we want a horse to start moving. The horse knows this command.
I searched the Internet. There is one mother who clicks her tongue, expressing her restlessness. There are children, too, who practice making a very loud sound out of it.
I don't have this habit, but maybe someone else has the habit and wants to tell in which situations they use it :)