What is the meaning of bind = True keyword in celery?

What is the meaning of bind=True in below celery code? When to use it and when not?

@app.task(bind=True)
def send_twitter_status(self, oauth, tweet):
    try:
        twitter = Twitter(oauth)
        twitter.update_status(tweet)
    except (Twitter.FailWhaleError, Twitter.LoginError) as exc:
        raise self.retry(exc=exc)

#python #django