Well, in Judaism and in Christianity, it is the star of King David, of whom Jesus was a direct descendant. Yep, Jesus is the Davidic King par excellence.
If you isolate the triangles, there is one pointing down and the other pointing upwards. The former symbolises God reaching down to man, and the latter man responding to God.
You can see the Star of David in many Churches, especially in Italy. One that comes to mind is the inferior Basilica of St. Francis where there is a pattern of stars under the arches of the entrance to the tabernacle place.
