When the feature is turned on, the operating system’s built-in voice will read out the name of the icon or whatever text that your finger is resting on. This will allow you to find the apps you need without even having to look at the screen. Once you’ve found what you need, you can simply lift your finger and give the icon a single tap to launch it. Scrolling up and down lists will require two fingers (since one-finger sliding is for identifying items).
This is just one video in a series of videos that will be highlighting the accessibility features on Android 4.0. Stay tuned to the Google Nexus channel on YouTube for more videos. In the meantime check out how the accessibility feature works: