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 6S is the most water-resistant iPhone to date. But don't take it in the pool with you. The iPhone 6S and iPhone 6S Plus have gained a number of new features over its predecessor, but one that Apple hasn't talked about at all is its attempts â and success â at making the new phone more water resistant.