Gaitors are those waterproof tubes that look a bit like big socks with the foot cut out. They attach to the top of your boot, and have a draw string at the top. A good pair of gaitors can turn your boots into an almost-welly. Practically speaking, this means that you don’t have to fling yourself out of the deep muddy puddle as quickly as you usually do (the speed of getting yourself out is critical because the longer you’re there, the deeper you go.) They’re also good in terms of keeping you all tucked in nicely. Trousers snag, get torn, get hooked on bits of kit. Gaitors stop all that.
But they are an extra piece of kit to carry, and again, for most of the year, a bit over the top. If you’re going rock climbing or ice climbing, then fair enough. If you’re going wild camping, probably a luxury.