Discharges refer to the release of substances from a system, and they can be categorized into several types. The most common types include liquid discharges, such as wastewater from industrial processes, and gaseous discharges, which involve emissions like carbon dioxide from factories. Each type can have different environmental impacts depending on the substances involved. Another important category is solid discharges, which include waste materials like plastics and metals. Additionally, thermal discharges occur when heated water is released into natural bodies, affecting local ecosystems. Understanding these types helps in managing and mitigating their effects on the environment.