Strictly speaking, a "shell" is simply the interface between the user and the rest of the operating system. In that definition not all shells on Linux are command lines.
However, most day-to-day usage of the term "shell" does refer to command line user interfaces.
Finally, "Linux shell" is not a thing. Linux is an operating system, specifically a kernel, not a shell. Most Linux distributions use BASH, but I personally prefer ZSH.
Neither one is strictly CUI (Character User Interface). Both can use a variety of user interfaces, notably that of an X server.
A shell in Linux is the interpreter that provides a commandline interface (CLI). There are many kinds of shells.
The Z shell is a Bourne-compatible shell for Linux and Unix systems.
bash (Bourne Again Shell) is the default shell in most Linux distributions. It was created as part of the GNU project.
Shell is the bridge between Kernel and User.
echo $SHELL
The courses available for Linux include Linux server, Linux desktop, bash shell, and many others.
Linux shell is a programming language. its fully different from others progrmming language. the script which is used in Linux quite tough to remember if we comparison to other programming laguages.
The shell.
C is a programming language. A shell is an interface.
To log into the system.
This is usually referred to as the "shell."