Terminal is where you interact with command line programs. In the image above I have used the program called `ls`, which shows the list of files and folders in my home folder. Terminal is also called "Command prompt" in some places.

Commands are not always available. A lot of complexity in programming is because the set of commands available on Linux, Windows and OSX differ. For example `ls` is not available on Windows by default. On Windows we have a command `dir` which performs similar function. To further complicate things, even if the commands are available they sometimes differ. Desipite these complications, they are not so bad, and are essential if you want to use the machine you have at the fullest. Writing command line applications are easier than building user interfaces so you will find a lot of functionalities are distributed as command line programs only, and not as GUI software you may be been used to so far. We have written a mini [guide on command commands: `fastn.com/cmds/`](/cmds/) you would want to use on a day to day basis which going through this book. Familiarise yourself with them, and come back to them on need basis. But do not bother too much about not knowing these commands or memorising them, they are best learnt incrementally, on a need to know basis, and we will be gradually learning about the commands you need while you are reading this book. Go on, issue the command `ls` or `dir` depending on which platform you are on. You will have to write the words `ls` or `dir` in the terminal or command prompt