A Loadable Kernel Module (LKM) is a piece of code that can be dynamically loaded into or removed from the Linux kernel at runtime, without needing to reboot the system. LKMs are commonly used to add support for new hardware, filesystems, or system calls, and they allow the kernel to be extended or updated without recompiling or restarting. While useful for flexibility and modularity, LKMs can also pose security risks if malicious modules are loaded, as they operate with high-level privileges and can alter kernel behavior. Proper management and verification of LKMs are crucial for maintaining system security.