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 next iPhone is just around the corner: The company is widely expected to announce a new model - a follow up to last year's iPhone 6 and 6 Plus - next month, unveiling it at a special event in California on September 9.