update v2/howto/cmd_parameter/index_en.rst (#9381)

* update v2/howto/cmd_parameter/index_en.rst

fix https://github.com/PaddlePaddle/Paddle/issues/8909/index_en.rst

* Update index_en.rst

update

* Update index_en.rst

fix punctuation & en.cmd

doc/v2/howto/cmd_parameter/index_en.rst

@@ -2,10 +2,25 @@
 
 Set Command-line Parameters
 ===========================
+The implementation of deep learning algorithms has a variety of characteristics, such as running environment, running stage, structure of the model and the traning strategy. PaddlePaddle supports the user to set various command-line parameters flexibly, which helps to achieve control of the model training or prediction process.
+
+In this part, we take several actual scenarios as an example, and the use of some command-line parameters is displayed:
 
 ..  toctree::
   :maxdepth: 1
 
   use_case_en.md
+
+Then, we summarize and classify the use of all command-line parameters:
+
+..  toctree::
+  :maxdepth: 1
+
   arguments_en.md
+
+Finally, the detailed descriptions are given, and we try to explain the propeties and significance of these command-line parameters in detail:
+
+..  toctree::
+  :maxdepth: 1
+
   detail_introduction_en.md