This is the inspector window. It is is Pages and Keynote and you use it to adjust things. To access different inspector panes you click the appropriate icon – document, text, shapes, rulers etc. Here’s a great tip: If you hold down option while clicking it will open a new inspector window alongside the existing one!
You can have more than one inspector window open at a time. Simply option-click the icon instead of clicking it and a second inspector window will open.
After the window opens you can move it where you want it to be.