Compilation errors occur when a program's source code cannot be translated into machine code by a compiler. These errors typically arise from syntax mistakes, such as missing semicolons, incorrect variable names, or mismatched parentheses. The compiler identifies these issues and provides error messages to help developers locate and fix the problems. When a compilation error is present, the program will not run until the errors are resolved. This process is crucial in programming languages like C++, Java, or Python, where the code must be error-free for successful execution. Addressing compilation errors ensures that the code behaves as intended.