When discarding or passing on equipment to others – a “factory reset” & even wiping of hard drive with permanent “military grade delete” is a best practice for safety.  Back up everything well & take time out to be safe before passing on to others.  Non-tech users should get help in process from a friend or relative in the know.  The holiday season is a peak time to pass on older devices to others.

What to do before selling, trading or giving away your iPhone or iPad | AppleInsider

You want someone to get a fresh iPhone or iPad, but you also want to be sure no one gets your data with it. Here’s how to make trading in, giving, or selling your iOS device painless for everyone.  If you’re giving your old iPhone or iPad to a relative, you’re going to get questions about it in return.  But for everyone else, you can prepare your iOS device so that it works for them like it came straight from the factory.  Clearly, that’s better for them, and clearly it also means you won’t then have to worry about any of your data being inadvertently left on the device. But what’s less immediately clear until it happens to you, is that preparing your old device correctly can help you with your new one.

How to remove your personal information from an old iPhone or iPad

    1. Go to Settings and tap on your name at the top
    2. Scroll to the bottom of the page that appears and choose Sign Out
    3. If prompted, choose Sign Out of iCloud and Store
    4. Otherwise, just tap Sign Out
    5. Enter your Apple ID password to confirm
    6. Tap Turn Off

That unplugs your iPhone or iPad from your iCloud and Store accounts, now you just have to get rid of any data of yours that’s physically on the phone. We’ll say it one more time, though: be sure you have a backup.

 How to delete personal information

    1. In Settings, choose General
    2. Scroll down to the bottom and tap on Reset
    3. Now tap on Erase All Content and Settings
    4. If prompted, enter your Apple ID and password
    5. Tap Erase