Instant is one of the many features Google has implemented over the last couple of years aimed at speeding up the world of search and works by populating your search results as you continue to type into the search bar and works brilliantly on the iPad. The iPhone’s smaller screen does reduce the impact of the constantly changing search results but it does work well.
More info from the official Google Blog:
Today we’re happy to let you know that Google Instant for mobile is now available in 28 languages and 40 countries worldwide. If you have an Android 2.2+ or iOS4 device, just go to google.com in your mobile browser and you will be redirected to your local domain. Then, tap the Google Instant link beneath the search box to enable it.
The only problem? Who actually visits Google.com anymore?!