In the left column of each MediaWiki page, you will see a small box labeled toolbox. The toolbox is very special. It typically contains things like:
But it doesn't stop there. The toolbox sort of "knows" where it is and can change to meet your needs while working on different types of pages. For example, if you are on your or another user's userpage, you may see something like:
This ability to adapt to different situations depending upon what namespace you're in, how your preferences are set, and other factors is called "context sensitivity". The best way to learn about the toolbox is to use the tools! As you navigate around, keep an eye on the toolbox and learn about all those special pages!