OLD:
In the old user interface all reports existed in the Reports-tab. Ribbon contained items for the standard reports, report shortcuts and recently opened reports. All reports (excluding recently opened reports) were also within the report gallery.
NEW:
In the new user interface reports can be found from Reports-menu. Five standard reports are listed first. User's recently opened reports, report shortcuts and custom designed reports can be seen in the Gallery which opens from the Report menu, too.
Gallery-page shows reports grouped to three sub-categories: recently opened reports, report shortcuts and custom reports. A report can be opened from the list by clicking the name.