iOS is the Operating System that runs on all the handheld Apple devices such as the iPhone, iPad (now called the iPadOS) and iPod touch.
If you want to know which version of the iOS software has been installed on your Apple device, you can find it out by going to the Settings App > General > About > Software Version
Let's see the above in screenshots:
- On the Home Screen - Tap on the Settings App,
- Locate General and Tap on it,
- Now Click on About,
- You should see the iOS version next to text - "Software Version"
- Tab on Software Version and you should see the built version as well
iOS Build Version List
|iOS Version||Build Version|
|15.1||19B74 / 19B75|
Read more: https://support.apple.com/en-us/HT201685