The Quick Access Toolbar (QAT) is located at the top left hand corner of the ribbon and has the most commonly used commands, like the Save, Undo and Redo. The QAT is unique to each user´s workbook settings.
You can move the QAT below or above the ribbon by right clicking on the QAT and making the selection.
You can also add your favourite commands to the QAT by right clicking on your favorite command in the ribbon and selecting Add to Quick Access Toolbar.
Finally, you can call your QAT commands by pressing the ALT key on your keyboard and then pressing the number (e.g. 1,2,3 etc) that appears at the bottom of that command.