Monolithic Kernel
A monolithic kernel is a kernel architecture where the entire kernel is run in kernel space in supervisor mode. In common with other architectures (microkernel, hybrid kernels), the kernel defines a high-level virtual interface over computer hardware, with a set of primitives or system calls to implement operating system services such as process management, concurrency, and memory management in one or more modules.
Microkernel
A microkernel is a minimal computer operating system kernel which, in its purest form, provides no operating-system services at all, only the mechanisms needed to implement such services, such as low-level address space management, thread management, and inter-process communication (IPC)