A text based I/O interface b/w user and the kernel.

Terminal emulation is software that emulates the function of a terminal. It allows the use of text-based programs within a graphical user interface (GUI). There are also so-called command-line interfaces (CLI) that run as additional terminals in one terminal

The most commonly used shell in Linux is the Bourne-Again Shell (BASH)

Besides Bash, there also exist other shells like Tcsh/Csh, Ksh, Zsh, Fish shell and others.

Taking Help

man <tool>
<tool> - -help (some tools may not give info with, but give with -h)
apropos <keyword> (This command list all the commands that has the keyword in the usage)

System Information

Commands	Description
`whoami`	Displays current username.
`id`	Returns users identity
`hostname`	Sets or prints the name of current host system.
`uname`	Prints basic information about the operating system name and system hardware.
`pwd`	Returns working directory name.
`ifconfig`	The ifconfig utility is used to assign or to view an address to a network interface and/or configure network interface parameters.
`ip`	Ip is a utility to show or manipulate routing, network devices, interfaces and tunnels.
`netstat`	Shows network status.
`ss`	Another utility to investigate sockets.
`ps`	Shows process status.
`who`	Displays who is logged in.
`env`	Prints environment or sets and executes command.
`lsblk`	Lists block devices.
`lsusb`	Lists USB devices
`lsof`	Lists opened files.
`lspci`	Lists PCI devices.

File Navigation

pwd - Prints working directory

cd - Change working directory

cd - - we can quickly jump back to the directory we were last in

cd .. - Jump to the parent directory

ls - list storage

ls -i - Shows index (or inode) number of the files