What's the purpose of an iPhone backup?

My iPhone 5 kept telling me that I was low on iCloud space for backup. I followed the directions and ended up deleting the backup. What's the purpose of it anyways? I'm so confused.

Well backup could be really good i something happens to your phone. Example: John have a iPhone 5 with many important stuff. One day he was on trip in France and someone stole his iPhone. The iPhone i locked so only John could open it. When he come home he bought a new iPhone and used the backup so the new iPhone look 100% like the one who got stolen.

The backup is for if you lost all your data on the iPhone(or lost the phone) you can restore back using the backup.

In case something was to go wrong with the phone you would have a backup to restore it from, including things like messages, app data, etc.

ICloud sets a free 5GB space limitation for every user, that is, you can use iCoud to store your backup free only when the backup is not more than 5GB. Or you will pay for more space. So it will prompt you that you are low on iCloud space for backup.

Personally, backup with iCloud is not so excellent except its conveniencee with wirelessly backup. You can use other tool such as iTunes to make backup, the space is not limited.

And iTunes can back up your settings, Messages, Camera Roll, documents, saved games, and other data. Backups do not contain content synced to the device, such as movies, music, podcasts, and apps.

As to your question, what's the purpose of an iPhone backup. There may be many cases where you can use your iPhone backup.

For example, when your iPhone is stolen or broken unfortunately, you can extract the data from the backup made before. And you can also make a backup( the backup can be viewed directly, just like a SD card storage) on your local PC then you can delete the data on your iPhone to get more space to restore other data.

But you need the tool to complete the data extraction and directly-viewed backup - iTunes Data Recovery windowspasswordsrecovery. Search it in the search engine.
Hope this helps you.