The labels of newt and salamander are often used interchangeably, and it's easy to understand why some people think these two distinct amphibians are the same animal. But there are, in fact, distinctions between the two.
Newts are a type of salamander, belonging to a subfamily called Pleurodelinae of the family Salamandridae. Essentially, all newts are salamanders, but not all salamanders are newts.
Beyond a name, how do you know if you're looking at a newt or a salamander? There are only a few subtle differences.
As adults, newts live a semi-aquatic to aquatic life, while adult salamanders live a mostly terrestrial life except for when they're breeding and laying eggs. Most newts have webbed feet and a paddle-like tail, which make it easier to live in the water. Salamanders typically have longer and more rounded tails with well-developed toes for digging in soil.
Even with these physical differences, the easiest way to know what you're looking at is to learn the individual species.
The amphibian in this photograph is a yellow-eyed ensatina, a salamander species native to California.