Newts are a type of salamander (like sea turtles are a type of turtle). They generally have rough skin while other salamanders have slimy skin. As far as I'm aware, all newts have lungs while some other groups of salamander do not. Newts also lack something called "costal grooves" which seems to be the best distinction I can think of. Costal grooves are these things:

http://www.uvm.edu/~kvbriggs/js/images/terms.html#costal