The kernel is the core component of an operating system that acts as a bridge between applications and hardware. When a system loads, the kernel loads first and remains in memory to perform low-level tasks like disk management, task management, and memory management. Kernels interface between hardware components like the CPU, memory, and I/O devices to provide services and manage computer resources, allowing other programs to run and access these resources. There are different types of kernels that vary in their implementation of operating system services.