From: https://www.loc.gov/preservation/digital/formats/fdd/fdd000525.shtml#signHEIF files containing HEVC-encoded images are also known as HEIC files
For a quite good technical explanation and examples, have a look at:.heic is used for HEIF file containing one or more HEVC coded image items. This is the format introduced by Apple in 2017 as an in-camera format for iOS devices. .heics is used for image sequences.