LG G Flex (2013): Curved Display
In 2013, LG introduced the first phone with a curved screen: the G Flex. The phone shared several features with LG's G2 smartphone, including a Qualcomm Snapdragon 800 SoC, 2 GB of RAM and 32 GB of internal storage. Its key features, though, were a 6-inch curved display and flexible plastic chassis. The 720p display drew criticism for having a relatively low pixel density of 245 PPI.
Incidentally, Samsung introduced its own smartphone with a curved screen around the same time, the Galaxy Round.
Apple iPhone 5s (2013): Enter The 64-bit Era
With the launch of the iPhone 5s in September 2013, Apple brought the smartphone into the 64-bit era. It was the first smart device to use the Apple A7 SoC, a dual-core model operating at 1.3GHz paired with a PowerVR G6430 GPU. It also contains the M7 coprocessor, which collects data from various sensors inside the device.
The iPhone 5s comes equipped with a 4-inch IPS screen with a resolution of 1136x640 (326 ppi), up to 64GB of storage, an 8 MP rear camera and a 1.2 MP front-facing camera. It supports 4G LTE and 802.11n Wi-Fi.
Its other claim to fame is Touch ID, a capacitive fingerprint sensor that's used to unlock the phone and authorize transactions. Fingerprint sensors are now a common feature on most mid-range and high-end phones.
The Personal Assistant: Siri, Now, Cortana (2011 - 2014)
The notion of a voice-based personal digital assistant hit the mainstream when Apple launched Siri back in 2011 with the iPhone 4S. Google followed suit with something similar with Google Now in 2012, although that service was more about marrying app usage, search and personal preferences into a series of information-based cards at your fingertips. In 2014 Microsoft released Cortana with Windows Phone 8.1, and its claim to fame was introducing contextual awareness and inference to the digital assistant, using an entity database Microsoft calls Satori. Further, Microsoft has extended Cortana onto the desktop, and there are apps for iOS and Android. The program has been criticized for excessive data gathering.