Adobe Lightroom has many ways of helping you get the most of your working space. These are called the Screen Modes:
- Full Screen with Menubar
- Full Screen
- Full Screen Preview
- Full Screen and Hide Panels
You can cycle through these by hitting the Shift + F key or you can go: Menu - Window - Screen Mode - Next Screen Mode to do the same.
The default Lightroom Screen Mode is the Normal mode and most users get stuck there.
With the Full Screen with Menubar you lose the minimize/maximize buttons and gain a little bit of space without losing the Menubar at the top.
With the Full Screen mode, you get the most space by losing the Menubar and the minimize/maximize buttons which leaves you with better interface to work on your photos. The Menubar is not really lost. It is like auto hidden and to get it back you just hover your mouse to the top of the interface.
If you want to just look at your selected photo and eliminate all interface distractions, just go to the Full Screen Preview (hit the F key). Press F again to go back to the last screen mode selected.