One of the many UI improvements Google has made in the latest version of Android 4.0 Ice Cream Sandwich is to expose commonly used buttons on a toolbar. This way, you don't have to use the hardware menu button (which, in fact, is hidden by default on the Galaxy Nexus) to dig into the menu anymore, but you can instead directly tap a persistently available button.
While that's nice, the icons shown in the toolbar don't have any text labels beneath them, which can make it hard to identify their meaning since they're often far from self-explanatory. However, there's an easy way to bring up a label.
Just press and hold an icon to bring up its text label, which clarifies the purpose of the icon. This works in most, if not all apps that are designed for Ice Cream Sandwich, of course including Google Apps such as Mail, Calendar, Talk, and Maps, but also various third-party apps (we've tested it in Dropbox, for instance).
It's a very thoughtful touch which shows that Google is finally starting to emphasize good design on Android, even if it is not as immediately apparent as on Windows Phone 7, where you can drag up the toolbar to reveal all labels.