The iPhone 12 was the first handset Apple has released to support 5G networks, with chips from Qualcomm. 5G will not necessarily be faster, but it will certainly assist with more connected devices and congestion, so for example in sports stadia you should see vastly improved performance.
This is the first year that Apple has released 4 iPhone models - the iPhone 12 Mini, iPhone 12, iPhone 12 Pro, and iPhone 12 Pro Max. The iPhone 12 mini - the return to a smaller form factor akin to the iPhone 5S, but with a full screen, full frontal, touch screen with face ID, is bound to be a huge seller, especially in the smaller hands Asian market.
A great new feature is the introduction of Mag Safe - expect a whole world of MagSafe chargers and cases, wallets and more, where the iPhone 12 can instantly "snap" to the accessory securely and safely.
Despite all these new features, not to mention all displays being OLED, The iPhone 12 series is actually cheaper than the previous years line-up. However - there is a catch. The iPhones do not come with earbuds or a power adaptor in the box, just a USB-C cable. The future is clearly not iPhones with USB-C ports, but iPhones with no ports at all, like the Apple Watch.