The ELN file format is an archive format for exchange of experimental results and data.
This file format can be created and read by software such as Electronic Laboratory Notebooks.
The file format is specified in the SPECIFICATION.md file.
This file format was created for the needs of better interoperability between ELN software. So editors of these software decided it would be useful for users to have an archive format that can be easily understood by several ELNs.
Generally working with some quirks here and there.