Add more info about example tags and _.py

docs/developers/contributing/documentation/index.md

@@ -798,7 +798,7 @@ If you prefer or need to use `make` (e.g., for headless builds), see the [advanc
 
 All of the examples in the [examples Gallery](gallery) are Python scripts that
 live under [the `examples` folder of the napari repository](https://github.com/napari/napari/tree/main/examples).
-Because of how this gallery is built, every such Python script needs a docstring
+Any example that should appear in the generated gallery needs a docstring
 containing at least a title (following the `.rst` format of docstrings in
 Python) and one or more _tags_. This ensures the example will be shown in the
 correct place in the table of contents for the gallery (see, for example, the
@@ -834,6 +834,31 @@ use of the `.. tags::` directive. In this case, the only tag associated with
 this example is `visualization-basic`. Multiple tags can be separated with a
 comma.
 
+Tags are generated into the [](tagoverview) pages by `sphinx-tags`. They are
+descriptive labels, not execution flags.
+Tags do not hide an example from the gallery or change how it is built.
+To stop displaying an example in the public gallery, 
+add an underscore _ after the example's name.
+microscopy_example.py would be displayed in the public gallery;
+while, microscopy_example_.py would not be displayed in the public gallery
+due to the trailing underscore in the name.
+
+Before creating a new tag, check [](tagoverview) and reuse an existing tag
+when possible. New tags automatically create new tag pages, so the tag set is
+easier to navigate when it stays small and intentional.
+
+The most common tags currently mean:
+
+- `visualization-basic`: introductory examples centered on core viewer or layer usage
+- `visualization-nD`: examples that focus on higher-dimensional, 3D, or multiscale data
+- `visualization-advanced`: more complex rendering, transforms, or advanced viewer composition
+- `gui`: Qt widgets, dock widgets, window integration, or other UI customization
+- `interactivity`: mouse callbacks, key bindings, and interactive viewer behavior
+- `analysis`: analysis, annotation, or measurement-oriented workflows
+- `layers`: examples that emphasize layer properties or layer interactions
+- `experimental`: examples that rely on experimental napari APIs or behavior that may still change
+- `historical`: legacy or reference examples that remain useful to publish, but are not the best starting point for new code
+
 Note that the examples are `.py` source files, and any outputs and images will
 be autogenerated when the documentation site is built.