The state of matter with a fixed volume and shape is solid. The particles of which a solid is made are tightly packed and rigid. They do not move from place to place.
Solid is one of three states of matter. The other two are liquid and gas. Liquids take the shape of their container but not necessarily the volume. The particles making up a liquid can flow easily, but there is little space between them. Gases take both the shape and the volume of their container. Particles in a gas flow easily at higher speeds, and there is ample room between them.