在导航抽屉中的返回语句是什么意思？

import * as React from 'react';
import { NavigationContainer } from '@react-navigation/native';
import { createDrawerNavigator } from '@react-navigation/drawer';
import { createStackNavigator } from '@react-navigation/stack';

const Drawer = createDrawerNavigator();
const Stack = createStackNavigator();

function HomeScreen() {
  return (
    <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
      <Text>Home Screen</Text>
    </View>
  );
}

function DetailsScreen() {
  return (
    <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
      <Text>Details Screen</Text>
    </View>
  );
}

function App() {
  return (
    <NavigationContainer>
      <Drawer.Navigator initialRouteName="Home">
        <Drawer.Screen name="Home" component={HomeScreen} />
        <Drawer.Screen name="Details" component={DetailsScreen} />
      </Drawer.Navigator>
    </NavigationContainer>
  );
}

export default App;