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 models in bold are the current flagship devices of the series: 1  iPhone (2007â2008) 2  iPhone 3G (2008â2010) 3  iPhone 3GS (2009â2012) 4  iPhone 4 (2010â2013) 5  iPhone 4S (2011â2014) 6  iPhone 5 (2012â2013) 7  iPhone 5C (2013â2015) 8  iPhone 5S (2013â2016)