So HEIF is for HEVC what WebP is for VP9.
Compared to this, HEIF is a different way of packaging HEVC frames; namely into ISOBMFF (MPEG-4 Part 12), the most basic level of MPEG container. This comes with benefits [2] that come along with using that particular container, but also drawbacks, because with some of the advanced features of HEIF you're essentially describing a sequence of frames -- which is almost like video -- but you're doing it in a way incompatible with the way you'd describe video. I'd be curious if the two "representations" are losslessly convertible, for example.
[1] https://bellard.org/bpg/ [2] https://nokiatech.github.io/heif/technical.html
They are: you could just extract the HEVC NAL units, and re-write them into a MP4 or QuickTime container, making sure to properly place the codec configuration box, etc.
HEIF also goes beyond a sequence of frames, in that it can describe alpha planes, depth maps, tiling, etc. In that case there might not be an analog with a standard video. If you really wanted to decompose a HEIF container, you might choose to extract the raw media into elementary streams (for HEVC or AVC; or if you're using the JPEG codec, just plain JPEG files) adjacent to any metadata like Exif, etc. This is essentially what Nokia's conformance files are [1].
[1] https://github.com/nokiatech/heif_conformance/tree/master/bi...
It's more like HEIF is for HEVC what WebP is for AV1.