Unlike our hardware components, I can't show you a photograph of the kernel as it's essentially a piece of software. There's nothing to look at!
The kernel pretty much constitutes the operating system, minus the software you install and use. Without a kernel, the rest of the system like the graphics and file systems can't exist let alone operate. So the kernel is pretty important.
When your system boots and the kernel is loaded into memory, it makes all the hardware attached to the system available to what's known as "user land". User land refers to the unprivileged "space" within the kernel that all software executes inside of. As the user, when you run software it generally "talks" to the kernel (from user land) and uses it to interact with hardware. The kernel operates as a (highly) privileged set of processes which can interact with hardware and do other very sensitive tasks.
Tasks like saving a file, talking to another computer over the network or rendering graphics to the screen (2D, 3D, games, etc.) all require going through the kernel.