The drop-down menus across the top of the site are used to select different sections of the site. They split the site contents by IP Office release and then language.
The selection you make in the left-hand drop-down drives the next drop-down and finally what information appears in the bottom section of the site.
Your browser remembers your last selection from each drop-down. It uses those values to automatically reapply your previous selections when you next return to a section of the site.