An interpreter is a computer program that executes the instructions written in a high level programming language. It can also preform the translation of a high level language to equivalent machine...
An interpreter, or a translator, is a person who translates different languages. For an example, if a Chinese person and an American person can't understand each other, an intepreter can translate...
As far as I know, an arms interpreter is someone who translates foreign languages for the army so that they can know why something is being done or what something is meant as.