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/.
The iPhone is the first smartphone model designed and marketed by Apple Inc. It is the first generation of iPhone that was announced on January 9, 2007, after years of rumors and speculation. It was introduced in the United States on June 29, 2007, and it featured quad-band GSM cellular connectivity with GPRS and EDGE support for data transfer. On June 9, 2008, Apple announced its successor, the iPhone 3G. After this announcement, the first-generation iPhone became referred to by some sources as the iPhone 2G because it had become the last iPhone to ship with the old 2G-speed EDGE network. The original iPhone has not received software updates from Apple since iPhone OS (now iOS) 3.1.3.