4 types of Linux kernels

"The Linux kernel is a free and open-source,: 4  monolithic, modular, multitasking, Unix-like operating system kernel. It was originally written in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system, which was written to be a free (libre) replacement for Unix." --Wikipedia

LTS Linux Kernel

The LTS (Long Term Support) is the most stable kernel. However, typically it will use older drivers which might not be compatible with newer hardware and might lack some features of the newer kernel releases. Long-term support (LTS) for Linux kernels is being reduced from six to two years.

Stable Linux Kernel

It is the latest stable release Linux kernel available and hence is the default kernel used by most distributions. It somewhat compromises stability for bleeding edge and therefore it is sometimes considered unstable in nature. (LTS) kernel available and is considered the comparatively ‘more stable’ than the default kernel.

Hardened Linux Kernel

It is the hardened version of the Linux stable kernel but is more security-tailored and comes with upstream patches before Linux does. It has a security oriented kernel configuration.

 

Zen Kernel

Zen is a kernel tuned for performance, aimed at improving performance of desktops at the cost of throughput and power usage. It is also sometimes considered the best kernel for gaming. It has a low latency and high-frequency scheduling. 

Conclusion

All Linux applications and servers also interface with the Linux kernel. A kernel is a computer program at the core of a computer's operating system. It enables multiple applications to share hardware resources by providing access to CPU, memory, disk I/O, and networking. Unlike the hybrid kernels of Microsoft Windows and Mac OS X, the Linux kernel is monolithic. Monolithic kernels control the CPU, memory, inter-process communication (IPC), device drivers, file system management, and system server calls.