iOS is one of the most popular operating systems on the planet, and it powers the iPhone, but what does that "I" stand for anyway? Here's what we know.

The iPhone's latest system upgrade is coming today. Here's when you can download iOS 18 and what it includes.

Apple iOS 18.6.1 is compatible with all iPhones from 2018 on. That’s the iPhone XS, iPhone XS Plus and iPhone XR models and every phone since. That means the iPhone 11 series, iPhone 12, iPhone 13 and so on right up to the iPhone 16 series, plus the second- and third-generation iPhone SE models as well as the iPhone 16e.

Also, when Apple released iOS 16.6 in July 2023 -- the last major iOS 16 update prior to the release of iOS 17 -- it was focused on bug fixes and security patches.

When Apple’s latest iOS 17 becomes available to the public on Monday, it brings the most significant new “wow” factor to iPhones to date.

All iPhones from the iPhone Xs onwards can run iOS 17. When does Apple Intelligence come out? iPhone users get iOS 18 now, but Apple Intelligence will not be a part of this update.