A "stub" is a term used in software development to refer to an incomplete part of a software or a function. Stubs are often used as placeholders to simulate or represent a specific functionality while it's not fully implemented yet. They can be used in various stages of development, such as early planning or during the integration of different parts of software. Stubs help developers to test or develop parts of software without having all dependent components available yet.

Stub files are files that serve as placeholders or caches and are commonly used in software development. They typically contain basic information, placeholder code, or references to other files or functions.

Generally, stub files are used when certain parts of a software are not yet implemented but are still needed to develop or test other parts of the program. For example, stub files can be used to define functions or classes that are intended to be implemented in later stages of development.

Stub files are particularly useful in large projects where multiple developers are working on different parts of the code. They allow developers to work independently on different parts of the system while still relying on each other to progress the overall project.