The "State of Matter" refers to the distinct forms that different phases of matter take on. The four primary states are solid, liquid, gas, and plasma. In a solid, particles are closely packed and vibrate in place, giving it a fixed shape. Liquids have more space between particles, allowing them to flow and take the shape of their container. Gases have even more space between particles, which move freely and fill the entire volume of their container. Plasma is a state where gas is energized to the point that electrons are stripped from atoms, resulting in a mixture of charged particles. Each state has unique properties based on particle arrangement and energy.