1)Suppose need to pass value from MainActivity to SubActivity.We will first make xml of both Activity:

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/etFirst"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter Name"/>
    <Button
        android:id="@+id/btnClick"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/etFirst"
        android:text="@string/click"
        android:layout_marginTop="20dp"/>
</RelativeLayout>



 activity_sub.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="value.com.valuebundle.SubActivity">
    <TextView
        android:id="@+id/tvShow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

2)Now in MainActivity,onCreate will be:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    etFirst=(EditText)findViewById(R.id.etFirst);
    btnClick=(Button)findViewById(R.id.btnClick);
    btnClick.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Bundle bundle=new Bundle();
            bundle.putString("first",etFirst.getText().toString());
            Intent intent=new Intent(MainActivity.this,SubActivity.class);
            intent.putExtras(bundle);
            startActivity(intent);
        }
    });
}

Here we are asking user to enter value in EditText and on a Button click,we are passing that value from MainActivity to SubActivity through Bundle and putting that Bundle in Intent.

3)Now in SubActivity,onCreate will be:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sub);
    tvShow=(TextView)findViewById(R.id.tvShow);
    Bundle bundle=getIntent().getExtras();
    String first=bundle.getString("first");
    tvShow.setText("welcome"+" "+first);
}

Here we have received the Bundle by Bundle bundle=getIntent().getExtras() and set it in TextView.

That's it.Hope it helps:)