Based on the thought leadership of Chris Argyris and Donald Schön as well as others along the way, here is an overview:
Single Loop Learning is about making adjustments to correct a mistake or a problem. It is focused on doing the things right. Causality might be observed but typically is not addressed.
Double Loop Learning is identifying and understanding causality and then taking action to fix the problem. It is about doing the right things.
Triple Loop Learning goes even deeper to explore our values and the reasons why we even have our systems, processes and desired results in the first place. It is about trying to ascertain an understanding of how we make decisions that frame our work.