Chief, the iCloud thing I mentioned above, you can set it to keep everything in your iPhone stored “in the cloud,” meaning in an Apple-controlled server somewhere. If you lose or replace your phone, you can download its mirror image — all the data, apps, etc. —to the new phone.
You can also remotely erase the contents of a lost or stolen phone.
While there are security implications to storing your data in the cloud, by which I mean you might at some point lose data to a hacker, I find the convenience worth it. (Hey, your bank , cc companies, etc., might get hacked and your data stolen, too. Gotta watch that stuff like a hawk.) You can also choose what to store, so I think you could choose not to store, say, your financial info, and just keep that locally.
I am sure Android phones have simething similar to iCloud with Google and perhaps other cloud services.
(The last time I had to recreate my contact list was moving from Blackberry to iPhone back when I retired six years ago. There must have been a more convenient way to do this than retyping, but I did not know what it was.)
If you use more than one Apple device, say an iPhone and an iPad, or an iPhone, iPad, and MacBook Pro, etc. — with iCloud, all the data, if you wish, will appear identically across all your Apple platforms (AKA gizmos) whenever you make a change on one.