The official Linden blog has a good article that includes the history but focuses on the usefulness of the “debug menu.” This is a menu that is not open by default in your SL software, because it does have the potential to, um, mess things up. I don’t recommend just mucking around in it. But Torley Linden explains “10 debug options you should know about” in such a way as to enhance your experience while keeping you safe. It’s at least worth knowing that “yes, you can do that.”
