To the right of the Audio Levels button is the Narrate Timeline button, which looks like a right side leaning microphone. When you select Narrate Timeline you are going to bring up the narration record window where you choose your settings and then record an audio track from your computer in Windows Movie Maker. The file is then treated as a regular audio file and saved to collections to be used in the secondary audio track.
To the right of Narrate Timeline are two separate buttons, each one a magnifying glass holding either a + or -. These are to zoom in and zoom out in the Timeline depending on what you want to do. In cases where you want to do fine clip trims you may have to zoom in, and when you are working on a larger project and want to see the entire Timeline in one view you will have to zoom out. This only affects the view of the Timeline and will not make any dramatic changes to your Windows Movie Maker project.