What exactly is a shell in Linux

Meaning of the "one" shell:

    First, the Shell's English meaning is "shell";

    It is relative to the kernel, because it is based on the kernel, a representation of the user, for example, we see a ball, see its shell, not nuclear.

    The shell in Linux, refers to a user-oriented command interface, the expression is a user input interface, the interface can also be feedback operation information;

The "two" shell exists in Linux in the form of:

    Since Linux is separate from the interface, unlike Windows,linux, it can be run out of the graphical interface, and it can also run a graphical desktop on the basis of the kernel.

    In this way, in the Linux system, there are two kinds of shell representation, one is the shell under the terminal environment without the graphical interface, and the other is the Windows-like MS-DOS running Windows running on the desktop, the former is generally referred to as the terminal, The latter is generally called the shell directly

How the "three" shell executes the user's instructions

   The shell has two ways of executing the instruction, the first is that the user writes a SH script file in advance, contains the shell script, and then executes the script using the shell program, which we are accustomed to call shell programming.

   The second form is that the user executes the shell command directly on the shell interface, and because of the shell interface, everyone is accustomed to writing a line of lines, rarely writing a complete set of programs to execute together, so also called the command line.

Summary: The shell can be said to be a bridge between the user and the machine, so that we can use the shell to operate and interact with the computer, so that the computer for us to serve the purpose.

What is a shell in Linux