How do the Ribbon buttons work?

In modern versions of Excel, the features provided by statistiXL can be accessed from a dedicated ribbon, depicted below. Date analysis modules are grouped into categories and can be accessed by the menu associated with each category button. Buttons are multifunctional; clicking on the bottom part will display the menu of modules associated with that category, while clicking on the top part will automatically re-open the most recently used module within that category.

How buttons work on the statistiXL tab in the Excel Ribbon