Help: Clarify target_sources PRIVATE/PUBLIC/INTERFACE scopes

Help/command/target_sources.rst

@@ -11,19 +11,21 @@ Add sources to a target.
     <INTERFACE|PUBLIC|PRIVATE> [items1...]
     [<INTERFACE|PUBLIC|PRIVATE> [items2...] ...])
 
-Specifies sources to use when compiling a given target.  Relative
-source file paths are interpreted as being relative to the current
+Specifies sources to use when building a target and/or its dependents.
+Relative source file paths are interpreted as being relative to the current
 source directory (i.e. :variable:`CMAKE_CURRENT_SOURCE_DIR`).  The
 named ``<target>`` must have been created by a command such as
 :command:`add_executable` or :command:`add_library` and must not be an
 :ref:`ALIAS target <Alias Targets>`.
 
 The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to
-specify the scope of the following arguments.  ``PRIVATE`` and ``PUBLIC``
+specify the scope of the items following them.  ``PRIVATE`` and ``PUBLIC``
 items will populate the :prop_tgt:`SOURCES` property of
-``<target>``.  ``PUBLIC`` and ``INTERFACE`` items will populate the
-:prop_tgt:`INTERFACE_SOURCES` property of ``<target>``.
-(:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.)
+``<target>``, which are used when building the target itself.
+``PUBLIC`` and ``INTERFACE`` items will populate the
+:prop_tgt:`INTERFACE_SOURCES` property of ``<target>``, which are used
+when building dependents.  (:ref:`IMPORTED targets <Imported Targets>`
+only support ``INTERFACE`` items because they are not build targets.)
 The following arguments specify sources.  Repeated calls for the same
 ``<target>`` append items in the order called.