A compiler error occurs when a programming language's compiler detects a problem in the source code that prevents it from being translated into machine code. This can happen due to syntax errors, such as missing semicolons or mismatched parentheses, which violate the rules of the programming language. The compiler provides error messages to help developers identify and fix these issues. These errors are crucial for ensuring that the code is correct and can run as intended. Common examples of languages that produce compiler errors include C++, Java, and Python. Addressing these errors is an essential step in the software development process.