Kernel is the most important part of the operating system.
An operating system in a computer is the software which manages the resources on the computer, It manages the user interaction (interface). It manages input and output devices. Examples are MS Windows, Linux, SunOS or Solaris, mobile OS for cell phones etc.
Kernel is the most important part of an OS. It is the central part of an OS. When a computer system is switched on, the operating system is loaded in to the memory.
Then the kernel takes control, initiates various tasks, initializes various input and output devices, checks memory and other components of the system. It initializes the windows, manages login and logout. It performs scheduled periodic tasks like reminders and initiation of backups. It takes care of clock on the system.
It allocates and manages the main memory of the computer. It manages the virtual memory on the disk. It does the user management. It provides multi-tasking, multi-threading and multi-user computing environment. It is the interface between user and the other devices like printer, mouse, disk, DVD etc.