Slider foods are foods that turn to mush or liquid in your mouth:-
Crackers
Chips
Popcorn
candy
Chocolate
Cake
Highly processed foods etc
They are high calorie, easy to overeat and have no effect on your hunger levels.
Non sliders are foods that are still relatively solid when they get to your stomach
Meat,fish,chicken,vegetables
They are full of nutrients and fill you up.