A toxin is a harmful substance produced either biologically or synthetically that can cause damage to living organisms. Toxins can come from various sources, including plants, animals, bacteria, and environmental pollutants. Their impact can vary widely, causing acute or chronic health effects depending on exposure levels and the organism's sensitivity. Understanding toxins is critical in fields such as toxicology, environmental health, and medicine, as this knowledge can help develop strategies for prevention, treatment, and regulatory policies to protect human health and ecosystems.