I received an email from Amazon about 2 phones I bought in the last 2 years, "Unlocked" but with AMZ ads :

"We wanted to provide you with an important update about your Prime Exclusive Phone.
Starting February 6, we will begin rolling out an Amazon Offers app update to disable lockscreen offers and ads on Prime Exclusive Phones. This will allow you to more easily use your phone's mobile unlock technology, as well as personalize your lockscreen with a photo or wallpaper.
When the Amazon Offers app update is available for your Prime Exclusive Phone, you can find it in the “My apps & games” section of the Google Play Store. Downloading this update will disable lockscreen offers and ads on your device. If you have enabled auto-updates in the Google Play Store, your phone will automatically update after you connect it to Wi-Fi.
Prime Exclusive Phones will still be available at a discount for Prime members and will be available unlocked, giving you the freedom and flexibility to choose the wireless carrier and service that best fit your need
s. Prime Exclusive Phones will continue to provide access to pre-installed Amazon apps, including the Amazon Widget app."

In a nutshell what does it mean?