Question Detail

NO, MainActivity is the default name for Android Projects Activity.

You can change it as your requirement and give it your own Name Also.

Index file in HTML or PHP that file is working as the first screen as default if you want to run page by domain name index file will call automatically.

But in Android Studio's MainActivity.java file mention in Manifest File  something like 

<application
    android:allowBackup="true"
    android:icon="@drawable/app_icon"
    android:label="@string/app_name"
    android:roundIcon="@drawable/app_icon"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>
....

</application>

???????

NO, MainActivity is the default name for Android Projects Activity.

You can change it as your requirement and give it your own Name Also.

Index file in HTML or PHP that file is working as the first screen as default if you want to run page by domain name index file will call automatically.

But in Android Studio's MainActivity.java file mention in Manifest File  something like 

<application
    android:allowBackup="true"
    android:icon="@drawable/app_icon"
    android:label="@string/app_name"
    android:roundIcon="@drawable/app_icon"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity"
        android:screenOrientation="portrait">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>
....

</application>

???????