A Bridging visa B (subclass 020) is for people who hold a BVA or BVB and applied in Australia for a substantive visa that can be granted while they are in Australia. You must be in Australia when you apply and when it is decided, and you give a reason, with supporting documents, for why you need to leave and return. The charge is A$575, with no extra charge for family members included in the same application.
Home Affairs says to apply no more than 3 months and not less than 2 weeks before you travel, and publishes no processing times. The travel facility may allow one trip or several until a specified date. If you are outside Australia when that date passes, the BVB ceases and you cannot return on it.