When I feel like changing things up, sometimes I'll make sliders with different combos of cheeses and sauces and condiments. Then I get to eat several different types of burgers instead of filling up on just one.
A change up is a pitch made to look like a fast ball with the same arm motion, but is gripped differently, and goes slower than a fast ball. A slider has its own spin and looks different from a fast ball, so it is not a change.