In short, it is a method that depends on accurate and frequent testing of the pool water in order to add only the specific ingredients needed to keep the water clear and sanitized.
BBB refers to bleach, baking soda and borax however those particular items may not be needed in your pool.
For example, I use liquid shock (just a strong bleach) and muriatic acid with an occasional addition of calcium via Calcium Increaser or more likely cal-hypo.
The most essential part of this is accurate testing. This requires one of two recommended brands of test kits, used daily or nearly daily.