heic is the abbreviation of High Efficiency Image File Format, which is a file format unique to Apple mobile phones. You can compress the picture files to be smaller in order to save storage space.
The following is a detailed introduction:
High Efficiency Image File Format (HEIF) is a container format for individual images and image sequences. It was developed by the Moving Picture Experts Group (MPEG) and is defined as Part 12 within the MPEG-H media suite (ISO/IEC 23008-12). MPEG claims that twice as much information can be stored in a HEIF image using HEVC as in a JPEG image of the same size, resulting in a better quality image. HEIF also supports animation, and is capable of storing more information than an animated GIF or APNG at a small fraction of the size.
HEIF files are a special case of the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12), first defined in 2001 as a shared part of MP4 and JPEG 2000. This file format standard covers multimedia files that can also include other media streams, such as timed text, audio and video.