In computing, a kernel is the low-level software that handles communication with hardware and general system coordination. Aside from some initial firmware built into your computer[he]#039[/he]s motherboard, when you start your computer, the kernel is what provides awareness that it has a hard drive and a screen and a keyboard and a network card. It[he]#039[/he]s also the kernel[he]#039[/he]s job to ensure equal time (more or less) is given to each component so that your graphics and audio and filesystem and network all run smoothly, even though they[he]#039[/he]re running concurrently. You don’t have to compile the Linux kernel but you can with this quick tutorial.

Source: LXer – How to compile a Linux kernel in the 21st century