Assuming you would like a blog post about the Settings icon on an iPhone's Home screen:
The Settings icon is one of the icons that comes standard on your iPhone's Home screen. When you tap it, it opens the Settings app, where you can change various settings on your device. Here, you can adjust things like your device's brightness, sounds, wallpaper and much more.
You can also manage your iCloud storage, connect to WiFi networks and Bluetooth devices, set up Do Not Disturb mode and more in the Settings app. In short, if there's something you want to change or adjust on your iPhone, chances are good that you'll find the option to do so in the Settings app.
If for some reason the Settings icon is missing from your Home screen, don't worry - simply go to the App Store and download it again. It's a free app that comes pre-installed on all iPhones for easy access to all of your device's settings in one place.