What is sanctuary and how safe is it really?

A number of churches around Australia offered sanctuary to a group of asylum-seekers - including children - at risk of being returned to the Pacific island nation of Nauru.

Tổng Giám Mục Anh giáo ở Brisbane là Peter Catt Source: AAP

The offer was led by the Anglican Dean of Brisbane, Peter Catt, and followed a failed High Court challenge by lawyers for the group, who say they risk abuse and trauma if returned to immigration detention on Nauru.

What is sanctuary, where does it come from and does it have any legal standing in Australia?