Android 4, also known as Ice Cream Sandwich, was a significant update to the Android operating system released by Google in October 2011. It aimed to unify the user experience across smartphones and tablets, introducing a more refined interface with features like a redesigned home screen, improved multitasking, and enhanced notifications. This version also brought new functionalities such as Face Unlock, allowing users to unlock their devices using facial recognition, and a revamped camera app with better photo editing options. Overall, Android 4 marked a major step forward in usability and performance for mobile devices.