what`s the two tags in the AndroidMenifest.xml used for

in the hello world project of android, there are some code in AndroidMenifest.xml that i am not really know what they used for.what`s the difference between action and category element. thanks in advance.

<开发者_高级运维activity android:name=".HelloWorld"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

This two tags are basically used for:-

1.ACTION_MAIN:- Start as a main entry point, does not expect to receive data. Please visit link

2.CATEGORY_LAUNCHER:- Should be displayed in the top-level launcher. Please visit this link

To all about the Action & Category constants please visit this link.