what's is a compiler

Answer 1

Something that "translates" the code you wrote in binary so the computer can understand it.
For example, if you write
cout << "Hello world" << endl;
Your computer won't understand it.
The compiler will now come and translate your code in binary (11010101001010 etc) so the computer can run your code :)

Answer 2

it converts source code ( the jibberish you wrote) into object code (the language the computer can understand). Before your program runs.

Answer 3

compiler is a type of language translator. which convert source code written in high level language into machine language