It seems that Pipfile / Pipfile.lock are intended to be replacements for requirements.txt, in the context of Python packaging. There isn't much documentation out there on how these actually work, however. I found an evolving description of pipfile on the PyPi section of the Python website here but it's pretty messy and doesn't explain the semantics of the different sections of the file.
Any pointers on how to understand these files?
It is worth noting that as of now (2022), pipfile and pipfile.lock are only used by pipenv, a tool written by the same authors. There is currently no standard (i.e. PEP) that mentions those files.
Regarding pipenv there's other popular tools (like poetry) that try to solve a similar use case without the use of pipfiles.
On a related note, there's also the dawn of pyproject.toml supported by various PEPs like 660 and 621, which is slowly gaining support by setuptools, flit, hatch.
Update: Since Summer 2022 the python packaging tutorial replaced the setup.py and setup.cfg based tutorial completely with pyproject.toml.
As explained above by @Charles Duffy, it is a direct analog of Gemfile and Gemfile.lock from the Ruby world. See reference below for more details.
Reference: https://medium.com/never-hop-on-the-bandwagon/gemfile-and-gemfile-lock-in-ruby-65adc918b856
