A kernel is the core component of an operating system, responsible for managing system resources and communication between hardware and software. It acts as a bridge, allowing applications to interact with the computer's hardware, such as the CPU, memory, and input/output devices. There are different types of kernels, including monolithic kernels and microkernels. A monolithic kernel handles all system services in one large block of code, while a microkernel runs most services in user space, aiming for a smaller and more efficient core. Examples of operating systems that use kernels include Linux and Windows.