Limb 1 - Yamas
The Yamas include 5 concepts for universal morality - practices for interacting with the world and everything in it (yourself included). They give us some insight into how to go about our Yoga practice both physically and mentally, as well as how to move through the world with the values of Yoga in mind.
Limb 2 - Niyamas
Similar to the Yamas, the Niyamas include 5 concepts, but this time they are personal - practices for observing and developing within yourself.
Limb 3 - Asana
This is the limb most of us are most familiar with - the physical practice of Yoga. Yoga Asana are the poses, transitions, movements and flows that we practice in order to keep our bodies well. This practice is also used to strengthen the bodies position as a conduit for deeper exploration of the mind, breath and spirit.
Limb 4 - Pranayama
Pranayama is the awareness, exploration and manipulation of the breath. Similar to Asana, there are countless techniques for adapting, observing and changing the breath in order to achieve a variety of different results. In essence, Pranayama gives us a closer connection to our bodies, mind and spirit through deepening the awareness within.
Limb 5 - Pratyahara
We start to take things even further inward with Pratyahara - withdrawal of the senses. Think of this as a transition from experiencing the outside world through the senses to gathering all of our awareness within ourselves.
Limb 6 - Dharana
Dharana is concentration - namely the practice of concentrating solely on one thing without interruption from the mind or body.
Limb 7 - Dhyana
Dhyana is a step further in meditation, where you become so deep in your practice that you are no longer conscious of the act of meditating, rather you are only aware of yourself and the thing that you are concentrating on.
Limb 8 - Samadhi
The state of Samadhi is the ultimate goal of Yoga - a state of one-ness with the self, the item of concentration, the universe. Consider Samadhi as a state of complete awareness and ease.