This document discusses kernel modules in Linux. Key points include: - Kernel modules can be loaded and unloaded at runtime to extend kernel functionality without recompiling. This saves memory and allows hardware-specific modules. - A basic "Hello World" module is presented to demonstrate initializing and exiting functions. - Compiling modules inside or outside the kernel tree is described. Tools for loading, uninstalling, and listing modules are also covered. - The document explains how to define module parameters and export symbols for other modules to use. Kconfig files are used to configure modules.