What effect does the linking of boards/projects have?

In Deck there is the option to link a board to a) projects or b) other boards.
However, I have not been able to find out what this linking actually does.
Can anyone give me a hint?
Thanks a lot!

This is a cross app Nextcloud feature.

You can also add Files to a project (from within the files app) or use projects in Talk. This way you can gather an overview to a specific topic with information and documents from various apps.