Not all applications have a Graphical User Interface (GUI) or visual component to allow the user to interact via point-and-click. Some applications are designed to be lightweight and accessible only through a command line. This is where we can directly access the Linux shell through text commands, using the Bash language.
The Terminal app is the default command-line interface that comes with Linux desktops (and MacOS). Inside the terminal, we can use commands to navigate the file system, move around files, and write files. In the command line, we can run applications that don’t have a visual component at all.
Several small terminal-based utilities provide system information such as the number of processes running, amount of memory currently being used, network configurations, and disk health. Some common examples of useful terminal utility commands on Ubuntu are:
Server applications also live in the terminal and can be configured there. These applications are the backbone of modern computing. These applications often run continuously in the background to provide a specific service like file sharing. Many of these server applications can often be controlled locally from the terminal or accessed remotely from another computer. Some common examples of server applications that can be found on a typical Ubuntu system are openSSH (secure shell server) and mySQL (database server).