Help: Document in add_library that IMPORTED_IMPLIB is for DLL import libs
Fixes: #21053
diff --git a/Help/command/add_library.rst b/Help/command/add_library.rst
index ed8447e..52536bb 100644
--- a/Help/command/add_library.rst
+++ b/Help/command/add_library.rst
@@ -144,7 +144,12 @@
References a library file located outside the project. The
:prop_tgt:`IMPORTED_LOCATION` target property (or its per-configuration
variant :prop_tgt:`IMPORTED_LOCATION_<CONFIG>`) specifies the
- location of the main library file on disk.
+ location of the main library file on disk. In the case of a ``SHARED``
+ library on Windows, the :prop_tgt:`IMPORTED_IMPLIB` target property
+ (or its per-configuration variant :prop_tgt:`IMPORTED_IMPLIB_<CONFIG>`)
+ specifies the location of the DLL import library file (``.lib`` or
+ ``.dll.a``) on disk, and the ``IMPORTED_LOCATION`` is the location of
+ the ``.dll`` runtime library (and is optional).
Additional usage requirements may be specified in ``INTERFACE_*`` properties.
An ``UNKNOWN`` library type is typically only used in the implementation of
