The iPhone's development being in 2004, under the code-name "Project Purple". The first generation iPhone was unveiled in January 9, 2007, along with the iPhone OS (now iOS).
All iPhone models does not have user-removable battery.
While both iPhone and iPod Touch models are similar, iPod Touch lacks the ability to use cellular network.
The original iPhone
The very first iPhone that is available in 2007. It featured quad-band GSM cellular connectivity with GPRS and EDGE support for data transfer.
It is powered by a Samsung's 32-bit RISC ARM SoC that is underclocked to 412 MHz from 620 MHz and is mated with 128 MB of RAM. It is available in 3 built-in storage capacities: 4 GB, 8 GB and 16 GB. It also has the 2.0 MP rear camera. It has the 3.5 inches display with 320×480 pixel resolution.
The original iPhone comes with iPhone OS 1.0. The last supported version for this phone is iPhone OS 3.0.1.
Introduced in June 9, 2008, it is the successor to the aforementioned original iPhone.
Specs wise, it is similar to the original iPhone except the cellular connectivity; iPhone 3G supports the UTMS/HSPDA connectivity. The iPhone comes with either 8 GB or 16 GB of storage.
The iPhone 3G comes with iPhone OS 2.0. The last supported version for this phone is iPhone OS 4.2.1.
The iPhone 3GS is the 3rd generation iPhone introduced in June 8, 2009.
While the body designed is the same as previous iPhones, it features the different hardware on the inside; Powered the phone is the Samsumg's S5PC100 SoC, which has the ARM Cortex A8 CPU and PowerVR SGX535 GPU. The SoC is mated with the larger 256 MB of RAM.
The rear camera is a 3.0 MP shooter that can records video at VGA resolution. The phone comes with either 16 or 32 GB of built-in storage.
It comes with iPhone OS 3.0. The last supported version for this phone is iOS 6.1.6.
The iPhone 4 is the 4th generation iPhone introduced in June 7, 2010. It is the first iPhone to have the different body design than its predecessors has.
It is powered by Apple's A4 SoC, which has the same CPU and GPU as the previous iPhone's SoC has. It is mated with 512 MB of RAM. It comes with either 8, 16 and 32 GB of built-in storage.
The GSM model has the Penta-band UMTS/HSDPA and HSUPA connectivity, while the CDMA model has the dual-band CDMA/EV-DO connectivity. Unlike previous iPhones, iPhone 4 use Micro-SIM card as opposed to Mini-SIM card.
The iPhone 4 featuring the better 3.5 inches IPS display with 960×640 resolution at 326 ppi. Apple refers to it as Retina display. The iPhone 4 has the 5.0 MP rear camera (which capable of recording HD videos) and 0.3 MP front camera.
The iPhone 4 comes with iOS 4.0 for GSM version and 4.2.5 for CDMA version. The latest supported version is iSO 7.1.2.
When it's released, it has some technical problems with the phone's antenna.
The iPhone 4S is the 5th generation iPhone that is introduced on October 4, 2011.
It is powered by the newer Apple A5 SoC with has the dual-core ARM Cortex-A9 CPU and dual-core PowerVR SGX543MP2 GPU. The phone supports the faster 14.4 Mbit/s HSPDA connectivity.
It has the bigger 8.0 MP rear shooter for still and video capture. It is capable of recording full HD video. The phone comes with either 8, 16, 32 or 64 GB of built-in storage.
The iPhone 4S comes with iOS 5. The latest supported version is iSO 7.1.2.
Introduced on September 12, 2012 and released on September 21, 2012, It is the 6th generation iPhone.
For the new iPhone, it use the Apple A6 SoC which features Apple's own dual-core ARM CPU and tri-core PowerVR SGX543MP2 GPU. The SoC is mated with 1 GB of RAM.
It is the first iPhone to supports LTE connectivity, and it utilizes Nano-SIM card. The phone comes with either 16, 32 or 64 GB of built-in storage.
The iPhone 5 comes with iOS 6. The latest supported version is iSO 7.1.2.
Released on September 20, 2013. It is the 7th generation iPhone. It is the high-end counterpart to iPhone 5C.
It is the first smartphone to be powered by a 64-bit ARM SoC; it is powered by Apple A7 SoC, which contain dual-core 64-bit ARM CPU and PowerVR G6430 GPU. For security, iPhone 5S also introduced Touch ID fingerprint recognition system.
It comes with either 16, 32 or 64 GB of built-in storage.
The iPhone 5S comes with iOS 7. The latest supported version is iSO 7.1.2.
Released on the same date as iPhone 5S was, it is the mid-range counterpart to the iPhone 5S.
It use the same Apple A6 32-bit SoC that was previously uses on iPhone 5. Instead of metal casing, it features the hard-coated polycarbonate body.
The iPhone 5C comes with either 8, 16 or 32GB of built-in storage. For OS the iPhone 5C comes with iOS 7. The latest supported version is iSO 7.1.2.
iPhone 6 and iPhone 6 Plus
Announced on September 9, 2014, the iPhone 6 and iPhone 6 Plus are the upcoming 8th generation iPhones.
Both model powered by the newer Apple A8 SoC, containing Apple's own dual ARMv8 CPU and PowerVR GX6650 GPU. Both models supports the newest LTE-Advance connectivity.
The difference between iPhone 6 and iPhone 6 Plus is the phone's size; iPhone 6 has the 4.7 inches body while iPhone 6 Plus has the 5.5 inches body. Both models comes with 16, 64 and 128 GB of built-in storage.
Both model comes with iOS 8 by default.