The Caudata are a group of amphibians containing the salamanders and all extinct species of salamander-like amphibians more closely related to salamanders than to frogs. They are typically characterized by a superficially lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults.

The first known fossil salamanders are from the Middle Jurassic. These salamander resembled modern mole salamanders in morphology and probably had a similar burrowing lifestyle. There are about 655 extant species of salamander.

A newt is a salamander in the subfamily Pleurodelinae, also called eft during its terrestrial juvenile phase. Unlike other members of the family Salamandridae, newts are semiaquatic, alternating between aquatic and terrestrial habitats over the year, sometimes even staying in the water full-time. However, not all aquatic salamanders are considered newts, however.

Newts metamorphose through three distinct developmental life stages: aquatic larva, terrestrial juvenile (eft), and adult. Adults have lizard-like bodies, return to the water each year to breed, and at other times live in humid, cover-rich land habitats.

Members of the family Salamandridae are mostly known as newts and lack the costal grooves along the sides of their bodies typical of other groups.

There are more than 100 known species of newts found in North America, Europe, North Africa and Asia.

Salamanders are amphibians characterized by a lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All present-day salamander families are grouped together under the scientific name Urodela.

Salamanders never have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin makes them reliant on habitats in or near water or in cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to the water intermittently, and others are entirely terrestrial as adults.

The skin of some species contains the powerful poison tetrodotoxin; these salamanders tend to be slow-moving and have bright warning coloration to advertise their toxicity. Salamanders typically lay eggs in water and have aquatic larvae, but great variation occurs in their lifecycles. Some species in harsh environments reproduce while still in the larval state.

Salamanders are most commonly found in the Northern Hemisphere and most species are found in the Holarctic ecozone (above 20° N. latitude), with some species present in the Neotropical zone (below 20 ° N. latitude in the Americas).

Unique among vertebrates, they are capable of regenerating lost limbs, as well as other damaged parts of their bodies. Researchers hope to reverse engineer the remarkable regenerative processes for potential human medical applications, such as brain and spinal cord injury treatment or preventing harmful scarring during heart surgery recovery.