I've been working on a Mac for around four months now, and never really had much reason to open up Terminal and use the command line interface (CLI), other than for starting and stopping Tomcat. Now that I've started trying to learn about Git, I'm using the command line more and more, and finding out new stuff daily, so I'm going to write the occasional post to share some of this info.
The operating system that most of us run on Macs is called OS X, and it's based on Unix. The way that one interacts with Unix is via a command shell, and the default shell for OS X is called Bash. It allows us to interact with our operating system without going through the graphical user interface (GUI) that sits on top of the OS. According to Wikipedia Bash stands for Bourne-again shell as it is a successor to the Bourne shell. So, when you open up Terminal, or iTerm which is an enhanced Terminal alternative, you are interacting with the Bash shell.