The lossy compressed HEIC format is based on HEVC (High Efficiency Video Compression), which was also developed by MPEG. Together with transparency and the ability to store more than one image, HEIC files can also contain 16-bit colors, whereas JPG files can only support 8-bit. HEIC files still have some compatibility issues, even though they are already posted and saved to social media or cloud storage as JPG images since they are automatically converted. Third-party apps or computer programs can still have difficulties interpreting HEIC files though. Luckily, you can disable saving images as HEIC on a iOS 11 device by going to Settings > Camera > Formats > Most Compatible, which will force iOS 11 to save images in the JPEG format. More information here heic to jpg converter