The tarp is not required, but gives a few benefits. First, it does offer more protection if you are camping on unusually rocky ground or with sharp sticks around. Second, this is probably the most beneficial point that it allows you to break camp without the need to wipe off the bottom of your tent with a towel to wipe off the moisture. Some people use it inside their tent if they are beach camping or if you don't want to sweep the tent out when you break camp.