django AsyncWebsocketConsumerについて

Question

AsyncWebsocketConsumerのドキュメントの下記のコードにおいて、groups=["broadcast"]の部分は何をしているのでしょうか？
この部分を削除しても問題なく動作するので、何が行われているのかがわかりません。ご教授お願いします。

from channels.generic.websocket import AsyncWebsocketConsumer

class MyConsumer(AsyncWebsocketConsumer):
    groups = ["broadcast"]

    async def connect(self):
        # Called on connection.
        # To accept the connection call:
        await self.accept()
        # Or accept the connection and specify a chosen subprotocol.
        # A list of subprotocols specified by the connecting client
        # will be available in self.scope['subprotocols']
        await self.accept("subprotocol")
        # To reject the connection, call:
        await self.close()

    async def receive(self, text_data=None, bytes_data=None):
        # Called with either text_data or bytes_data for each frame
        # You can call:
        await self.send(text_data="Hello world!")
        # Or, to send a binary frame:
        await self.send(bytes_data="Hello world!")
        # Want to force-close the connection? Call:
        await self.close()
        # Or add a custom WebSocket error code!
        await self.close(code=4123)

    async def disconnect(self, close_code):
        # Called when the socket closes