The Apple A12 Bionic is a 64-bit ARM-based system on a chip designed by Apple Inc., part of the Apple silicon series, It first appeared in the iPhone XS and XS Max, iPhone XR, iPad Air, iPad Mini, iPad and Apple TV 4K. From Wikipedia
Apple's upcoming software update will feature a major design overhaul and advanced features exclusive to newer devices, leaving older models on iOS 18 with security updates.