The kernel is the privileged core of an operating system. It manages memory, schedules processes, controls access to devices and provides system calls that applications use to request services such as file access or networking.
Ordinary applications generally run with fewer privileges than kernel code. When a program reads a file or sends data across a network, it relies on the kernel and its drivers to perform those operations while enforcing isolation between processes.
Kernel bugs can have unusually serious effects because the affected code has high privilege. A faulty driver may cause a system-wide crash, and an exploitable vulnerability may allow an attacker to escape application-level restrictions. Not every operating-system component runs in the kernel, however.
Keep kernels and drivers updated through supported distribution or vendor channels, test critical updates before broad rollout and plan recovery for systems that fail to boot. Reducing unnecessary privileged components also reduces the potential attack surface.