A slider is an American term for a small sandwich, typically around two inches (5.1cm) across, served in a bun.
Over the weekend, a dear friend and his wife invited me and friends to the opening of their restaurant. On the menu, was grilled sweet and sour pork chops with grilled pineapple slices, which I love. While I was enjoying the meal, my friend, seated next to me, kept picking at my pineapple slices. She loves grilled pineapple.