If you have never read it, then you should brew some of your favorite coffee, sit down, and treat yourself to reading Neal Stephenson's essay "In the Beginning Was the Command Line." You can download a copy from his web site, in the form—appropriately enough—of a raw text file:
The "command line" is the topic of this chapter: how you can access it over the network, together with enough discussion about its typical behavior to get you through any frustrations you might encounter while trying to use it.
Happily enough, this old-fashioned idea of sending simple textual commands to another computer will, for many readers, be one of the most relevant topics of this book. The main ...