You hear about them once in a while at your occasional yoga class but today I learned the true importance of the three bandhas (and discovered there were 6 more!): Mula Bandha (Pelvic Floor or "Root" Lock), Uddiyana Bandha (Abdominal or "Flying" Lock) and Jalandhara Bandha (Throat Lock).  All three (and ultimately 9) are all energy locks in the body mostly at joints or epicenters/intersections of important muscle groups that, once engaged, are responsible for the support needed to perform postures safely and of course, allow for the supreme Kundalini (serpent) energy to rise through your chakras for nirvana.  But for those of us still figuring out how to root ourselves to the earth, the bandhas really provide the counter resistance to gravity that is going to get you through a sequence with all the support needed without expending too much energy.  Try it: particularly Mula Bandha (which has the double-benefit of improving your sex life): now imagine contracting your pelvic floor, anus and (if you have one), vagina and transverse abdominals everyday, all the time.  It's amazing to have this level of intuition and constant awareness of the body...whilst preserving good health as it is a great preserver of energies as well.  80% of yoga-related injuries have to do with coming out of postures improperly and not having this support system of locks in place when releasing or transitioning from a pose...note that, along with the way it will definitely enhance your performance.