A compiled language is one where the source code is translated into machine code by a compiler. This machine code is specific to the type of machine it is compiled for, meaning the same compiled code cannot be run on different types of machines without being recompiled. This process differs from interpreted languages, where the source code is not directly converted into machine code but is instead read and executed by an interpreter, which allows for cross-platform compatibility. Compiled languages are known for their performance efficiency because the machine code is executed directly by the computer's hardware.