The Phone is a device in which you store very personal data like contacts, images etc. So personal device should be secure so that no one can access your personal data.
On 10 September 2013, Apple launched iPhone 5S with extra & unique fingerprint scanner feature to provide extra security. That scanner is hidden inside the round home button. Apple has advantage of this feature because till now no Smartphone companies provide security of that extent. Now iPhone has a better chance to stand against android market.
Once the user stored his finger impression in device, he will be unable to unlock iPhone by pressing round home button. This fingerprint impression may also be used in apps. To buy apps user just provide his fingerprint impression or Touch ID. Apple claimed that sensor used for scanning fingerprint could scan at 550 PPI (Pixels per Inch) resolution. Users can store more than one fingerprint impression on his device, so that anyone you can trust also use your cell phone. Apple also claimed that this fingerprint impression is saved on A7 chip inside iPhone 5S, not on iCloud or Apple servers, because according to a leaked report of NSA, NSA has the capability to access iCloud.