Definition of Matter:

Physical substance in general, as distinct from mind and spirit  

Fun fact: Matter is composed from atoms 

SOLID: 

A solid has a definite shape and volume because its particles are tightly packed and held in fixed positions by strong intermolecular forces. Solids are incompressible and maintain their shape unless acted upon by an external force

An empty cup

LIQUID: 

Liquids have a definite volume but no fixed shape, allowing them to flow and take the shape of their container. 

water

GAS: 

Gases have neither a definite shape nor a definite volume. Their particles are far apart and move freely, filling the entire space of their container.  

Hot air Balloon