The equals sign means is equal to. It is telling us that one thing equates to another; that they are the same.
The iPhone 4 is the most recent iPhone to be discontinued from the iOS Update cycle. It did not receive the iOS 8 update, so it's final software version is iOS 7.1.2. You can update to this version through iTunes, or download it from an IPSW repository like this website: https://ipsw.me/.
Apple's latest iPhones have one unmistakeable feature: size. The iPhone 6 is has a 4.7-inch display, and the iPhone 6 Plus jumps to 5.5 inches. Both have Retina HD displays with a curved body and NFC chips for Apple Pay, but the iPhone 6 Plus includes optical image stabilization with its 8-megapixel camera.