Documentation: explain resolutions example

The example given here

https://yarnpkg.com/lang/en/docs/selective-version-resolutions/#toc-how-to-use-it

is entirely opaque. What is the problem motivating this example? Why are there three versions of left-pad? What are file:../c-1, file:../d2-1 and why are they used here? What is c/**/left-pad and why is different to d2/left-pad?

As this is one of the suggested workarounds for #4986 it would be helpful if the example were clearer. I imagine many people encountering this are, like me, not very familiar with the arcana of dependency specification.