add submodule explanation

Author: TheRealOwenRees

README.md

@@ -14,9 +14,11 @@ Run the following commands from inside the project root directory to install the
 
 ```shell
 npm install
-git submodule update --init --recursive
+git submodule update --init --recursive # add/update a local copy of the problem-specification submodule
 ```
 
+To automate the creation of practice exercise tests, our track tooling consumes data from the the [problem specifications][exercism-problem-specifications-link] submodule. Because these specifications serve as the canonical source for all Exercism tracks, any upstream updates ensure our test cases remain consistent with the global exercise standard.
+
 If you have format on save enabled for JSON files, it is recommended to disable this feature. Alternatively save JSON files with `Ctrl+K s` to save without applying formatting rules.
 
 ### Running the development environment
@@ -149,3 +151,4 @@ If you find this documentation is inaccurate or incomplete, or can be improved i
 [github-fork-pr-link]: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request-from-a-fork
 [exercism-pr-docs-link]: https://exercism.org/docs/building/github/contributors-pull-request-guide
 [exercism-contributing-docs-link]: https://exercism.org/docs/building
+[exercism-problem-specifications-link]: https://github.com/exercism/problem-specifications