TalkBack

TalkBack provides spoken feedback for eyes-free computing.
TalkBack is an Accessibility Service that helps blind and vision-impaired users interact with their devices more easily.
This application add spoken, audible, and vibration feedback to your device. It is a system application that was pre-installed on most device and is updated when the accessibility service is improved.
This app is only activated if you explicitly turn on Accessibility.

Steps to activate Accessibility:
1. Go to Settings
2. Select Accessibility
3. (Android 3.2 and earlier) Enable Accessibility checkbox
4. Enable TalkBack checkboxes
5. (Android 4.0 and later) Enable explore-by-touch