The jhanas are eight progressive altered states of consciousness that can be identified with the aspect of the Buddha's Eightfold Path called Right Concentration. Training in concentration leads to these states, each of which yields a deeper and subtler state of awareness than the previous one. The jhanas are not in themselves awakening, but they are a skillful means for stilling the mind in a way that leads in that direction. Jhana practice is helpful for gaining the deep insights necessary for ending personal suffering. This introductory talk describes the states and how one would go about learning them and applying them.
Bonus: Leigh also briefly discusses his new free-to-download book on Dependent Origination and Emptiness (http://sodapi.leighb.com)