what is a compiler

what is it? i know you type pretty c++ or w/e code and it converts it into computer language so computer knows waht we mean, how do they differ for different languages asides that they convert two different languages? (its kinda hard to explain what im asking) like if all it does is change what we do to computer language for any programming language, why can't we have 1 universal programming language

omfg when they said for people to read it they didn't mean publish a fucking book, the lvl of code at that point is ment for a human to comprehend so they can give the machine better instructions. as in the human would read c++ code, and understand and read that better than they would fucking binary making it easier to give better instructions. and if there were no computers, we'd remake them then give instructions.