Add basic layer modes description ('pan_zoom' and 'transform')

docs/guides/layers.md

@@ -28,6 +28,24 @@ currently supported by napari, check out the
 introduction, check out the
 [Layer list section in the napari viewer tutorial](layer-list).
 
+(layer_mode)=
+## Layer mode
+
+All our layers support a `mode` property that changes the way you interact
+with the layer from the viewer. These modes are accesible via the layer controls widget top buttons and via shortcuts (pressing a number from `1` to the number of modes available for the layer). Depending on the layer type, more modes could be available. Currently, there are two base modes: Pan and zoom (`pan_zoom`) and Transform (`transform`):
+
+* Pan and zoom
+![image: Pan/zoom](../images/pan-zoom-tool.png)
+
+The `pan_zoom` mode allows you to pan around and zoom in/out the layer. It's the default mode selected.
+
+* Transform
+![image: Transform](../images/transform-tool.png)
+
+The `transform` mode allows you to translate, rotate, and scale the layer graphically. To reset the transformation, you can Option/Alt-click the transform button over the layer controls (a confirmation dialog will open to confirm the reset).
+
+For a more detailed description of layer modes available check each [layer how-to guide](using-layers).
+
 ## Layer visibility
 
 All our layers support a visibility toggle that allows you to set the `visible`

docs/howtos/layers/shapes.md

@@ -171,7 +171,7 @@ are used. i.e. You can't remove a vertex before you have created a shape.
   than one shape, select one, hold down the shift key and select the rest.
 
 * **Pan/zoom**
-  ![image: Select shapes](../../images/pan-zoom-tool.png)
+  ![image: Pan/zoom](../../images/pan-zoom-tool.png)
 
   Use this tool to pan around the image or zoom in. Pan and zoom functionality
   is disabled when using the adding and editing tools. Temporarily re-enable pan