* Liquids: Take the shape of their container. Think of water in a glass, a bottle, or a puddle. It flows and conforms to the shape of the container it's in.
* Gases: Fill the entire space available to them. Imagine air in a balloon. The air expands to fill the whole balloon. If you let go of the balloon, the air will escape and spread out in all directions.
Solids, on the other hand, do have a definite shape because their molecules are tightly packed and arranged in a fixed pattern.
