It's important to back up your iPhone before doing any major restores (such as a DFU restore). If something goes wrong while you're trying to fix your iPhone, having a back up means you won't lose any of your data (such as contacts, photos, apps, and more). Restoring from a back up is a lot more convenient than having to go and reenter all the information that was saved on your iPhone.

How Do I Back Up My iPhone?

There are a few different ways to back up your iPhone:

Backup Your iPhone Using iCloud

If you have a WiFi connection, you can back up your iPhone using iCloud.
Open the Settings app.
Tap on Your Name at the top of the screen.
Tap iCloud.
Scroll down and tap on iCloud Backup.
Make sure the switch next to iCloud Backup is on. You'll know the switch is on when the switch is green.
Tap Back Up Now.
A status bar will appear to tell you how much time is remaining.

Backup Your iPhone Using iTunes

Plug the Lightning connector on your Lightning cable (charging cable) into the Lightning port on your iPhone.
Plug the other end of your Lightning cable into a USB port on your computer.
Open iTunes on your computer.
Click on the iPhone icon in the upper left hand corner of iTunes.
Click the circle next to "iCloud" or "This computer" to select whether you want to backup your iPhone to iCloud or your computer.
Click Back Up Now to backup your iPhone.
When the backup is complete, you'll see the time and date updated under Latest Backup.

Backup Your iPhone Using Finder (Macs Running Catalina 10.15 or newer)

Connect your iPhone to your Mac using a charging cable.
Open Finder.
Click on your iPhone under Locations.
Click the circle next to Back up all of the data on your iPhone to this Mac.
Click Back Up Now.
When the backup is complete, you'll see the time and date updated under Latest Backup.