The kernel is the central component that connects the hardware to the software, and manages the system's resources, such as memory, CPU, and time sharing among competing applications and services. It handles all the devices that are connected to the computer by including so-called device drivers and makes them available for the operating system to use.
A system running only a kernel has limited functionality, and the only place you will see that is in a dedicated device (often termed as an embedded device) such as inside an appliance.

An Operating System includes the kernel and some additional components like User interface, File system, Utilities Tools and Security. It is a software that manages computer hardware and software resources and provides common services.

To distinguish, the Kernel is the part of the Operating System and the Operating System itself include many more components. In addition, users interact with the Operating System, but Kernel operates in the backstage.