Highlights:-

video calling and photo calling.
Scratch resistant oleophobic surface.
Accelerometer sensor for auto-rotate.
16/32 GB storage, 512 MB RAM.
LED flash , out focusing.

Specifications:-

GENERAL	2G Network	GSM 850 / 900 / 1800 / 1900
	3G Network	HSDPA 850 / 900 / 1900 / 2100
	Announced	2010, June
	Status	Available. Released 2010, June
SIZE	Dimensions	115.2 x 58.6 x 9.3 mm
	Weight	137 g
DISPLAY	Type	LED-backlit IPS TFT, capacitive touch screen, 16M colors
	Size	640 x 960 pixels, 3.5 inches
		- Scratch-resistant oleophobic surface - Multi-touch input method - Accelerometer sensor for auto-rotate - Three-axis gyro sensor - Proximity sensor for auto turn-off
SOUND	Alert types	Vibration, MP3 ringtones
	Loudspeaker	Yes
	3.5mm jack	Yes, check quality
MEMORY	Phonebook	Practically unlimited entries and fields, Photo call
	Call records	100 received, dialed and missed calls
	Internal	16/32 GB storage, 512 MB RAM
	Card slot	No
DATA	GPRS	Class 10 (4+1/3+2 slots), 32 - 48 kbps
	EDGE	Class 10, 236.8 kbps
	3G	HSDPA, 7.2 Mbps; HSUPA, 5.76 Mbps
	WLAN	Wi-Fi 802.11 b/g/n, Wi-Fi hotspot
	Bluetooth	Yes, v2.1 with A2DP
	Infrared port	No
	USB	Yes, v2.0
CAMERA	Primary	5 MP, 2592 x 1944 pixels, autofocus, LED flash
	Features	Touch focus, geo-tagging
	Video	Yes, 720p@30fps, LED video light, geo-tagging
	Secondary	Yes, videocalling over Wi-Fi only
FEATURES	OS	iOS 4
	CPU	1 GHz ARM Cortex-A8 processor, PowerVR SGX535GPU, Apple A4 chipset
	Messaging	SMS (threaded view), MMS, Email, Push Email
	Browser	HTML (Safari)
	Radio	No
	Games	Downloadable, incl. motion-based
	Colors	Black, White
	GPS	Yes, with A-GPS support
	Java	No
		- MicroSIM card support only - Scratch-resistant glass back panel - Active noise cancellation with dedicated mic - Digital compass - Google Maps - Audio/video player and editor - Voice command/dial - TV-out
BATTERY		Standard battery, Li-Po 1420mAh
	Stand-by	Up to 300 h (2G) / Up to 300 h (3G)
	Talk time	Up to 14 h (2G) / Up to 7 h (3G)
	Music play	Up to 40 h

Comparison between iphone4 and iphone3

The special feature in iphone4 is provided with the secondary camera (or) the front camera which is used for video calling and photo calling new technologies implemented which where not present in the iphone3.

This is provided with 5mp camera and the old iphone3 is only provided with 3.5mp camera

The major difference is network accessing new iphone4 is 4G accessing and iphone3 is 3G accessing and look differ by a lot.

Video of iphone4 :-