A compiler error.
Well let me first start off what a compiler is.
A compiler is a tool to scan through your code and catch syntax errors and other errors that you can miss or create when you type (Due to carelessness or just typos).
A compiler error (As I think you’re not talking about the program’s compiler but the code) it will be an error that is detected in your code. It will lead you to the line, sometimes you have to go all throughout your code to correct the error others it can be as simple as forgetting to put a semicolon at the end of the line.