Compiler
When you don't speak someones language, you can use a translator to help you with that. That is the compiler!
It receives a Programming Language as an input, and converts it to machine readable, low level code. The input is usually made in High level languages such as C, Java and Python. And the ouput is usually binary, consisting of 0's and 1's.
JavaScript is not considered a programming language, instead it is a scripting language.
This adds the benefit of being able to write in multiple languages, but having them all to be ran by the machine, since they get translated, or more specifically "compiled".
There are also compilers that don't convert code to machine code, instead they convert code from one language to another. They are called "Transpilers".