Most of the buttons are readily recognizable as to their purposes such as formatting text, paragraphs and so on. The Link button is especially important in creating documentation because it let's quickly create links that will take the reader to other parts of the document. For example, I will link this topic to the Tools topic. I just highlight the word Tools and click the Link button The link feature even intelligently guess the topic I want to link to and selects that topic for me.
Next to that button is a tool to let you quickly insert Internet links and next to that is a button to let you insert images into your help file. Further to the right, the Camera icon is also one you will likely use very often since it launches the Help and Manual integrated screen capture tool.