Notes are an integral part of the InCopy/InDesign editorial workflow as per @Frans v.d. Geest and provide a way to include inline comments within InDesign that flow with the text as per @Laubender.
You could write notes to yourself (I tend to use the first pasteboard for that) but I see them used primarily to communicate with others co-working on a document. The key is to using them successfully is to work with View > Extras > Show Notes enabled and let others in the workgroup know to be on the lookout for them.
So @BobLevine —this came up in class the other day. They are only converted to PDF sticky notes if exported from InCopy but not from InDesign? I meant to look it up but since you are here... 😬
well, to insert notes to text that will not print.
The notes can be made visible fully written out in InDesign's Story Editor window and of course in the Notes panel. Here a sample from my German InDesign 2025:
Some script writing folks, including me, are even able to move or duplicate formatted text programmatically in and out of notes.
To take up space on the toolbar for the 3% who find it useful.
Or, through a rather convoluted and limited process, add 'editorial notes' to a project. Despite the fundamenal usefulness of that function, it's so clunky I gave up after trying to use it a couple of times.
The tool bar needs revision and/or/better customizability. Even MS Office lets us rearrange the ribbon and strip out the marketing-wow default options.