A software application is a way that a computer’s operating system talks to its hardware. A computer’s hardware is managed by a number of software programs that run on the computer’s operating system.

Application/System Library 

System libraries are specialized applications that facilitate interaction with the kernel. Applications are responsible for initiating a job in the kernel. Every kernel has its own unique set of system calls, thus applications need to know how to make one. A standardized set of protocols for talking to the kernel has been compiled by the programming community. All OSes translate these specifications into their own system calls, so they can all work together. Glibc is the most well-known Linux system library (GNU C library).

Shell

Depending on the kind of user interface they provide, operating systems may be categorized as either graphical shells or command-line shells. An interface between the user and the operating system kernel is called a graphical shell. It offers kernel services, and it conducts kernel activities. There are two distinct varieties of graphical shells, each with its own distinct look. The graphical shells and command-line shells are the two distinct types of user interfaces that are used by these operating systems. While the command line shells enable for command line interfaces, the graphical line shells enable for graphical user interfaces. As a direct consequence of this, both of these shells are functional. On the other hand, graphical user interfaces that are carried out with the assistance of graphical line shells are much quicker than those that are carried out with command line shells. 

Kernel

When talking about operating systems, one of the most important components is the kernel. It performs every essential function of the Linux OS. Linux’s fundamental operations are all coordinated directly with the hardware. The kernel is responsible for developing a suitable abstraction to hide unimportant hardware or application techniques. Types of kernels are Monolithic Kernel, Micro kernels, Exo kernels, and Hybrid kernels.

Hardware

Linux’s hardware layer consists of the computer’s central processing unit (CPU), hard disk drive (HDD), and random access memory (RAM).