Index: llvm/docs/TestingGuide.rst
===================================================================
--- llvm/docs/TestingGuide.rst
+++ llvm/docs/TestingGuide.rst
@@ -528,16 +528,16 @@
 **Clang-specific substitutions:**
 
 ``%clang``
-   Invokes the Clang driver.
+   Invokes the Clang driver for plain C.
 
 ``%clang_cpp``
-   Invokes the Clang driver for C++.
+   Invokes the Clang driver as a C/C++ preprocessor.
 
 ``%clang_cl``
    Invokes the CL-compatible Clang driver.
 
 ``%clangxx``
-   Invokes the G++-compatible Clang driver.
+   Invokes the G++-compatible Clang driver for C++.
 
 ``%clang_cc1``
    Invokes the Clang frontend.