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/.
They run Apple's iOS mobile operating system. The first generation iPhone was released on June 29, 2007; the most recent iPhone model is the iPhone 7, which was unveiled at a special event on September 7, 2016. The user interface is built around the device's multi-touch screen, including a virtual keyboard.