Salamanders may not be the most appealing creatures to us, as they may appear dirty and slow-moving, but they play an essential role in our ecosystem by contributing to ecological balance. With about 5,000 species known today, salamanders belong to the class Amphibia, which means they can live in both water and on land. They have slender bodies, stout noses, and long tails. Fossil species are classified under order Caudata, while living species fall under order Urodela. Their forelegs have four toes, while their hind legs have five toes. Their skin is well-suited for living in both aquatic and terrestrial environments. Some species live entirely in water or on land, while others prefer a combination of both. They have a remarkable ability to regenerate body parts.

Mature salamanders have a lizard-like appearance, while some have an eel-like body with reduced limbs. They do not have claws, and some species are brightly colored year-round, while others only become brightly colored during the breeding season. Some prefer to live underground and lack skin pigment, resulting in white or pink body coloration. Some species are quite small, such as the minute salamanders that measure only 2.7 cm in length. Conversely, some species can grow quite large, such as the Chinese giant salamanders that measure up to 1.8 m in length and weigh up to 65 kg. Most species measure between 10-20 cm in length. Salamanders shed their skin to grow and consume the shed skin. Respiration varies among different species, with some breathing through gills in the absence of lungs. Gills are visible as hairy tufts on either side of the head, while amphiumas have both internal gills and gill slits. Terrestrial species breathe through lungs, but the structure of their lungs is much simpler compared to that of mammals. Olms have both gills and lungs, while some species breathe through their skin in a process known as cutaneous respiration.

Their skin secretes a large amount of mucus, which helps keep them moist when they move on dry land. The mucus also helps maintain salt-water balance and acts as a lubricant during swimming. Skin glands secrete poison and pheromones during courtship, and the tip of their tongue is kept moist with mucus to aid in prey capture. Some highly aquatic species lack muscle in their tongue, making it unsuitable for prey capture. Most species have teeth in both their upper and lower jaws, and they use trichromatic color vision in the ultraviolet range for prey capture. Subterranean salamanders have reduced eyes covered with a flap of skin. Some highly aquatic species have a lateral line system, similar to that of fish, for detecting pressure changes. External ears are absent, and the middle ear is vestigial. When attacked by predators, they can shed their tails, which later regenerate through a process called autotomy. They can also regenerate damaged limbs.

Salamanders can be found on all continents except Antarctica, Australia, and most of Africa. North America is home to one-third of all known species, with the Appalachian Mountains hosting the highest population of salamanders in the world. They prefer to live in moist habitats, such as creeks, ponds, and brooks, in arid and dry areas of the northern hemisphere. Their life history is similar to that of frogs and toads. In most species, fertilization is internal, with the male depositing sperm contained in sac-like structures inside the female's cloaca. Females are oviparous, laying eggs near ponds or on moist soil. Ovoviviparous species are also known.