Solid-liquid equilibria refer to the state where a solid and its corresponding liquid coexist at a specific temperature and pressure. This balance occurs when the rate of melting of the solid equals the rate of solidification of the liquid. The phase diagram is a useful tool for visualizing these conditions, showing the regions where different phases are stable. In many materials, such as water or salt, solid-liquid equilibria are crucial for understanding processes like freezing and melting. These equilibria are influenced by factors such as temperature, pressure, and the presence of impurities, which can alter the melting point and other properties of the substances involved.