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 5s is now the old generation iPhone with the unsurprising arrival of the iPhone 6. A new Apple smartphone means changes so here's where we compare the iPhone 5s and iPhone 6 to explain the difference between the two including price, features, performance and specs. See also: Best smartphones of 2015.