Sounds really intriguing, right?
So lets see what it is.
What is a HEIF file?
Here you can see how to open and save heif/heic files to JPEG on Android devices - How To View HEIF/HEIC files on Android
With Luma Android app you can convert heic images to common jpeg format and preview heir files stored on your device.
The app for viewing heic files is available in Google Play Store:
More about HEIC/HEIF file format https://fileinfo.com/extension/heif