Welcome to LQ!
One good place to check is The Linux Documentation Project
Another is to try and type "info" at a command prompt and it usually brings you into the info utility where you can learn about commands. Also if you type "man <command>" such as "man dd" you get the manual page on the command specified.
For scripting there are many guides, here are some:
- blog entry on bash programming
- Bash Scripting Guide for Beginners
- Advanced Bash Scripting Guide
I also found a pretty good cheat sheet by searching under google for "Linux command line" http://www.cheatography.com/davechil...-command-line/
Be careful with dd by the way, that is a way to byte for byte copy from one place to another; typically examples employ the use of root or sudo (same as root) because you need those higher privileges to perform disk copies. The caution is that the destination "of=" could accidentally be your working disk if you type that unintentionally or copy a command word for word not knowing the details of what it really will perform.