The purpose of a kernel in an operating system is to manage system resources and facilitate communication between hardware and software components. It serves as the core interface that controls how applications access hardware resources like memory, CPU, and input/output devices. By managing processes, handling system calls, and ensuring security, the kernel plays a crucial role in ensuring stable and efficient operation of the system. Different types of kernels, such as monolithic, microkernel, and hybrid, offer varying levels of complexity and capabilities.