Activity drawer - a slide-out box that displays +1s and reshares (pictured below). Just click on the set of mini icons and thumbnails on the right just below posts.
Application - features and destinations, such as "Home," "Profile," "Pages," "Hangouts" and so on are now called "applications" or "apps."
Card - the box that contains posts and everything that goes with it (comments, plus ones, shares, action buttons, menus, third-party browser extension links like "Translate," etc.
Explore - a new page or "application" that shows you a variety of stuff that might interest you, including "Who to follow," "What's Hot," and presumably other stuff in the future.
Ribbon - "Applications" sit in a strip of real estate on the left called the "ribbon."
Please study these. There will be a quiz tomorrow. ; )