Now we get into typing more than one command. These are all the different ways you can run mkdir. What's mkdir do? It make directories. Why are you asking that? You should be doing your index cards and getting your commands memorized. If you don't know that "mkdir makes directories" then keep working the index cards.
What does it mean to make a directory? You might call directories "folders." They're the same thing. All you did above is create directories inside directories inside of more directories. This is called a "path" and it's a way of saying "first temp, then stuff, then things and that's where I want it." It's a set of directions to the computer of where you want to put something in the tree of folders (directories) that make up your computer's hard disk.
In this book I'm using the / (slash) character for all paths since they work the same on all computers now. However, Windows users will need to know that you can also use the \ (backslash) characters and other Windows users will typically expect those at times.
For the price of most other course's PDFs only, you can get the full PDF for this class and 2 videos demonstrating the whole book for both Unix/OSX Terminal and Windows PowerShell. The course is self-paced so you can go through it any time you want, as many times as you want.