An object file is a binary file produced by a compiler after source code is compiled. It contains machine code, which is the low-level code that a computer's processor can execute. Object files also include metadata, such as symbol tables and relocation information, which help link the code with other object files or libraries during the linking process. Typically, object files have a specific format, such as ELF (Executable and Linkable Format) or PE (Portable Executable). These formats define how the data is organized within the file, allowing tools like linkers and loaders to understand and manipulate the code effectively.