iOS 9, with a redesigned user interface
iOS 9 comes with a slightly revamped user interface, including a new font typeface. It keeps much of its design from its immediate predecessors, but comes with performance and battery improvements across the board.
Revamped multitasking
Switching between apps looks noticeably different, helping users see what's going on inside apps. Performance wise, it's faster on the latest iPhone 6.
Long live the battery!
Finally, iPhone and iPad users have their very own dedicated battery settings section to help manage their device's power. In recent years, iPhone users have complained a declining battery life.
Improved Spotlight search
Spotlight now comes with a prepopulated list of contacts, apps, nearby places, and other relevant information. It also brings you an at-a-glance look at the news.
Long live the battery!
iOS 9 users have a new "low power mode," which helps cut down on heavy battery use. That includes fetching email messages manually, reducing motion effects, and turning off animated wallpapers.
Siri can now do a lot more
Siri got a little bit smarter. The assistant now digs into a number of new sources you’re your device data to your surroundings. In many cases, it prefetches information before you even ask for it. You can now search for things on the fly from a touch of a button.
Siri powers intelligence searches
Apple's answer to Google Now, the voice-activated assistant can now take on more complex queries. You can even ask it to remind you when to leave home or work depending on the traffic, or show you photos between a date range.

Photo search queries
In this case, you can ask Siri to return photos from a set time period, from a specific location, or from the past week or month.
Better passcode security
Apple devices no longer have the four-digit passcode, used to encrypt the devices, unless you specifically opt for it. The new standard is six-digits, which significantly cuts down on brute-force attempts.
Better passcode security
Users have the option to use a strong alphanumeric passcode, a custom length numeric code, or the old trusty favorite, a four-digit numeric passcode.
Maps now come with public transit maps
Apple Maps come with public transit maps, such as subway or Tube maps, helping you to get around major cities and other transport links.
Maps now come with public transit maps
At a glance, it's easy to see when trains or other transport links will arrive.
Maps now come with public transit maps
The improved Maps app can even point you to where the subway entrances are so you can shave off those vital minutes.
Split-screen mode for iPads
Following in the footsteps of the Surface tablet, latest iPads can now use "split view" to have two apps open and active at the same time. It's one step closer to true multitasking.