CSS media queries establish breakpoints for altering the layout according to screen width. Through CSS alone the navigation menu can be stacked vertically for very small screens or spread out to a horizontal bar. Some rearranging is done by manipulating widths and display modes.
Pages have breadcrumb navigation as well as links to adjacent content. The navigation menus up top are made by Processwire's versatile MarkupSimpleNavigation module. Current methods for detecting touch screen devices are not 100% reliable so we always show icons you can tap to open submenus. All of these are automatically maintained.
Items are individual things in the catalog. Groups are collections of items.
Different kinds of groups and items can be established with different handling and styling.
You can add groups and items one at a time using forms in the admin interface or use the versatile Flexo Sql Import module for importing group and item information in bulk from MySQL database tables.
Let us know what you are interested in.