The Quick Access Toolbar contains a set of commands that are independent on the tab (Home, Insert, Page Layout, etc.) that is currently displayed. The default location of the quick access toolbar is upper-left corner next to the Microsoft Office button. You can move the quick access toolbar from one of the two possible locations. One is upper-left corner next to the Microsoft Office button i.e, above the Ribbon (see the 1st image) and another is below the Ribbon (see the 2nd image). To move the quick access toolbar from above the Ribbon to below the Ribbon just click on the quick access toolbar i.e, small button looks like arrow near the Microsoft Office button and choose Show Below the Ribbon. Similarly is you wish to move it to near the Microsoft Office button and choose Show Above the Ribbon.
You can customize quick access toolbar yourself. You can add more shortcut buttons in the quick access toolbar and remove them simultaneously. There are 28 popular commands and overall almost 1586 commands in the All Command category list.
To add more shortcut buttons click in the quick access toolbar and then click More Commands.... Word Options window opens. You can do it another ways also. Click Microsoft office button and click Word Options and then click Customize located left side of Word Options window. Select the commands that you want to add in the quick access toolbar and click Add located center of the window. Similarly you add more commands in the quick access toolbar. Finally you need to click OK to save your changes.
If you wish to remove any commands from the quick access toolbar do the above process and select the commands from the list located right side pane and click Remove and then click OK to save changes.