Matter exists in different forms known as the phases of matter, primarily categorized into solids, liquids, gases, and plasma. In solids, particles are closely packed and vibrate in place, giving them a definite shape and volume. Liquids have particles that are close together but can move freely, allowing them to take the shape of their container while maintaining a fixed volume. Gases consist of particles that are far apart and move rapidly, filling the entire space available to them without a fixed shape or volume. Plasma is a high-energy state where electrons are separated from atoms, commonly found in stars, including our Sun. Each phase has unique properties based on particle arrangement and energy levels.