An amphibian is a type of cold-blooded vertebrate that typically lives both in water and on land. They belong to the class Amphibia, which includes frogs, toads, salamanders, and newts. Amphibians usually start their life cycle as aquatic larvae with gills and later undergo metamorphosis to develop lungs for breathing air. Amphibians have moist skin that helps them absorb water and breathe, making them unique among vertebrates. They play important roles in ecosystems as both predators and prey. Many amphibian species are sensitive to environmental changes, making them indicators of ecosystem health.