improve electrode group documentation

Author: h-mayorquin

core/nwb.ecephys.yaml

@@ -235,7 +235,10 @@ groups:
 
 - neurodata_type_def: ElectrodeGroup
   neurodata_type_inc: NWBContainer
-  doc: A physical grouping of electrodes, e.g. a shank of an array.
+  doc: A physical grouping of electrodes, e.g., a shank of an array. An electrode group is typically used to describe
+    electrodes that are physically connected on a single device and are often (but not always) used together for
+    analysis, such as for spike sorting. Note that this is descriptive metadata; electrodes from different groups
+    can still be spike-sorted together if needed.
   attributes:
   - name: description
     dtype: text

docs/format/source/format_release_notes.rst

@@ -32,6 +32,10 @@ Minor changes
 - Made ``EventDetection.times`` optional and deprecated. Use `source_idx` instead. (#620)
 - Clarified documentation of ``PlaneSegmentation`` that at least one of ``image_mask``, ``pixel_mask``,
   and ``voxel_mask`` is required. (#636)
+- Improved documentation of ``ElectrodeGroup`` to clarify its purpose as a physical grouping of electrodes
+  that are typically used together for analysis, such as spike sorting. (#631)
+- Specified that units for ``ElectrodesTable`` coordinate fields (``x``, ``y``, ``z``, ``rel_x``, ``rel_y``, ``rel_z``)
+  should be in microns. (#659)
 
 2.8.0 (November 24, 2024)
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