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/.
In fact, you might be surprised to learn that the second most used iPhone on the planet is the iPhone 5s, a device that was released all the way back in 2013. Broken down by model, here are the most used iPhone devices as of Saturday, February 6. iPhone 6 â 35.06%. iPhone 5s â 19.1%. iPhone 6s â 13.73%.