The third jhana is significantly different from the first and second in many ways, and is probably the most important jhana to understand, since it basically turns everything you think about meditation and progress on its head, thus causing endless confusion and frustration for meditators who don't know what it is about and what to look for, and even for plenty who do. From a certain perspective, understanding the third jhana is the key to mastery, whether that mastery is of concentration practice, insight practice, or a fusion of the two.
