For generations, we've told children about the amazingly entertaining effects of static electricity. Rubbing two charged objects together causes electrons to flee from one to the other, giving a uniform negative charge to one side, and a uniform positive charge to the other — leading to the delightful hair-raising, wall-sticking results.
Now scientists have finally managed to pick apart what actually happens when you do those grade school experiments, and unfortunately our explanations have not been quite right. Kelvin probe microscopy allows researchers to scan the microscopic hills and valleys that cover any object and reveal their electrical charge. What researchers found is that rather than a complete change in charge over the entire object, both items had pockets of both positive and negative charges — but one had more of one type than the other.
So rather than an overall charge over the entire surface, the difference is that one object has more islands of negative charge, and the other has more islands of positive.
Now you have the information to be the pedantic family friend who corrects kids when they tell you what they learned at school today!