diff --git a/Doc/source/ttLib/ttFont.rst b/Doc/source/ttLib/ttFont.rst
index 3034a6104..c3a41ba78 100644
--- a/Doc/source/ttLib/ttFont.rst
+++ b/Doc/source/ttLib/ttFont.rst
@@ -21,10 +21,56 @@ font file, or it may be a member of a
 constructed from scratch. 
 
 In addition to font-wide data, :mod:`.ttLib.ttFont` provides access to
-individual glyphs through the :class:`.TTFont` object's
-``glyphSet[]``. This is a dict-like object that is indexed by glyph
-names. Users can use the glyphSet to interact with each glyph's
-contours, components, points, and glyph metrics.
+individual glyphs through a :class:`.TTFont` instance's
+``glyphSet[]`` attribute. A ``glyphSet`` is a dict-like object that is
+indexed by glyph names. Users can use the glyphSet to interact with
+each glyph's contours, components, points, and glyph metrics.
+
+
+ttGlyphs
+--------
+
+Informally, some fontTools code or documentation will make reference to
+the individual glyphs in a ``glyphSet`` as a "ttGlyph" or the
+like. This is convenient terminology, particularly for
+discussion. However, it is important to note that there is not a
+"ttGlyph" class. Instead, the ``glyphSet`` attribute of a
+:class:`.TTFont` serves as an abstraction layer that provides a
+uniform interface to the glyphs, regardless of whether the
+:class:`.TTFont` instance in use comes from a font file with
+TrueType-flavored glyphs (and, therefore, has a `glyf` table
+containing glyph contours) or a font with PostScript-flavored outlines
+(and, therefore, with a ``CFF`` or ``CFF2`` table containing the glyph
+contours).
+
+Regardless of the flavor, each "ttGlyph" entry in the ``glyphSet``
+includes the corresponding Bezier outlines and components from the
+``glyf`` or ``CFF``/``CFF2`` table and the glyph's metrics. Horizontal
+metrics are drawn from the font's ``hmtx`` table, and vertical metrics
+(if any) are drawn from the ``vmtx`` table. These attributes are:
+
+width
+    The advance width of the glyph
+
+lsb
+    The left sidebearing of the glyph
+
+height
+    (For vertical-layout fonts) The advance height of the glyph
+
+tsb
+    (for vertical-layout fonts) The top sidebearing of the glyph
+
+Note that these attributes do not describe the bounding box of the
+glyph filled shape, because the filled area might include negative
+coordinate values or extend beyond the advance width due to overhang.
+
+The bounds of the glyph are accessible as ``xMin``, ``xMax``,
+``yMin``, and ``yMax`` attributes.
+
+For implementation details regarding the different flavors of
+"ttGlyph", see the :doc:`ttGlyphSet </ttLib/ttGlyphSet>`
+documentation.
 
 These glyph objects also implement the :doc:`Pen Protocol
 </pens/index>` by providing ``.draw()`` and ``.drawPoints()``