If you tried jumping on a bed without gravity, you would just keep floating up until you hit the ceiling. But, gravity pulls you down and makes sure you don't fly up.
Gravity keeps you stable on the ground or surface you're standing on and won't let you be pushed up. The gravity bond between a person and the bed attract and pull each other to keep from separating very far.
Without friction, all of these books would just slide off the desk. But, the friction between the books and desk keep it stable without moving. The only way it would fall off is if an outside force contacted it and pushed it off.
With elasticity, the rubber band is hurled across the room easily. The more force you use to pull it back, the farther it will fly.
Without elasticity, the rubber band wouldn't move very far and just fall to the ground. Without the pull on he band, there is no opposite force that will make it fly forward.
Magnetism is when magnets attract same forces and come together. Magnets could attract metals and have them stick together. If you hold opposite magnets together they will repel each other and it wouldn't work.