In the google search console's list of indexed pages for my site there are many urls like this:
https://www.stakeholdermap.com/project-templates/change-management-plan-pdf/?SD
https://www.stakeholdermap.com/project-templates/_notes/?SD
https://www.stakeholdermap.com/plan-project/images/?SA
These aren't real pages and I have made sure they go to my custom error page. I am just wondering what they are? That is, what is google seeing that it wants to index?