Let's start with don't try this at home kids!
He may be a Russian Redneck... Either way, somebody in Russia posted video of a guy sitting in the grass at what looks like a construction site . . . and he's using an angle grinder on one of his toenails.
It looks like he's trying to remove some grit from the top of the nail. Whatever he's doing, the person shooting the video thinks it's pretty funny.