A Makefile is a special file used by the make build automation tool to manage the compilation and building of software projects. It contains a set of rules and instructions that specify how to compile and link the program's source code files. By using a Makefile, developers can automate repetitive tasks, ensuring that only the necessary parts of the project are rebuilt when changes are made. Makefiles are commonly used in programming languages like C and C++, but they can also be adapted for other languages. They help streamline the development process, making it easier to manage complex projects with multiple source files and dependencies.