Complex sentence: Carols by Candlelight is an Australian Christmas tradition that has spread around the world, that involves people gathering, usually outdoors in a park, to sing carols by candlelight, accompanied by a band.
Split into simpler sentences: Carols by Candlelight is an Australian Christmas tradition that has spread around the world. It involves people gathering, usually outdoors in a park, to sing carols by candlelight, accompanied by a band.