"Chrome" is a term used to describe the components surrounding the content in an application. Your operating system has chrome (like the taskbar), as do individual applications -- even websites will have their menus and modes. Having consistent chrome is important because it lets users quickly access frequently used tools and to access the state of the program.
But sometimes the chrome really takes over and hides the content itself:
Granted, this is quite an unusual scenario that occurs relatively infrequently, but is important to consider. When designing a single application or application component it's difficult to see how layers of interfaces stack up on top of each other like this.