What is a kernel?

At the very basic, a kernel can be described as an important central component that works as a linking point between user applications and the processing of data found at the hardware platform.  A kernel is an extremely important part of your operating system.

The hardware that the kernel connects to from application's needs include many of the core pieces that make up your computer including for example, the brain of your system, the Central Processing Unit (CPU) and also memory for storing data. 

In addition to the CPU and memory allocations, a kernel also manages your input/output devices.  These are the devices that you connect to your computer or laptop to either give data like a mouse or keyboard or to receive data like a printer or monitor.

The kernel is the one that controls and manages the resources mentioned above...the CPU, I/O devices and memory.  Through process management, processes or threads are executed.  Your computer at any moment can be processing many threads.  All the threads need access to the CPU.  Each thread is given an equal amount of time to process.  This rule of sharing is called the O(1) scheduler.  Without this scheduler, only one process can be performed at a time.

There are many operating system kernels available now.  Generally, they each perform the very basic of functions for what they were originally intended for.  What sets them apart is additional features which are becoming more widely available as each day goes on.  Some features that seem to be getting more attention today relates to security, integrated firewalls and debugging.