An interjection used to draw attention or urge someone (like 'look, look!' or 'come on'). Can be admonishing or friendly depending on tone.
ほらほら、電車が来るよ。急いで乗って。
Look, the train's coming. Hurry and get on.
ほらほら、そんなところで立ち止まってないで早く来て。
Come on, don't stand there — hurry up and come.
ほらほら、言ったでしょ？忘れ物をするって。
See? I told you you'd forget something.
子供が遊んでいるのを見て、親が『ほらほら、転ぶよ』と注意した。
Seeing the child playing, the parent warned, 'Look out, you'll fall.'