Classical yoga under Patanjali has 8 different "limbs" of yoga! The first "limb" is the Yamas or social contracts. The second "limb" are the Niyamas or contracts with oneself. The third "limb" is Asana or yoga poses, there are hundreds!
Spell "yoga" backwards and add in an "n" you get "agony", well that's what asana can be to some! Thats what it was like to me when I began taking yoga classes. My body would be in pain and then one day it stopped. One day I could tie my shoelaces again, I could stand on one leg, I could do a handstand! I was flabbergasted. I had not done that for 40 years! Thank you asana. Thank you all my asana teachers!
Agnistambasana or "ankle to knee" pose to me is agony! As well as other poses that my body simply will not allow me to come into! My hips are tight! My shoulders are tight! My thoracic spine is tight! My psoas muscle is tight! My hamstrings are tight! Yet for 6 years now I have practiced yoga and slowly, like water dripping on a rock, changing the shape of the rock, my body as gotten stronger, more flexible and like a 12 year old I can do handstands, headstands and other various yoga/asana poses.
Asana or poses, are what most people connect with "yoga" some skinny looking god or goddess in what looks like an unimaginable pretzel anatomical position available most probably only to snakes!
Asana or poses, are many. There are standing poses, arm balances, forward bends, back bends, side bends, side twists, inversions, sitting poses, etc. There are so many. A balanced practice or class will most probably incorporate all!
Everybody's body is different! The length from your shoulder to your wrist! From your shoulder to your elbow is different! The length from your hip to the base of your foot! From your hip to your knee is different! For most of us.
From your belly button to your chin! From the top of your skull to the base of your foot, we are all physically different which means each asana/pose will be different for each of us.
Think of the asana/pose as a container which is made up of three parts:
Foundation, alignment and breath! (FAB)
A house needs a strong foundation to stand firm and strong. Asana foundation is that part of the pose that touches the floor!
Alignment is important just like an airplane wings shape is important!
During take off an landing it extends in size and curves more so it has more "lift" thus permitting it to take off and land at slower speeds! Alignment in asana/pose is equally important for example the knee should be over the ankle and centered in warrior 2 pose to protect the knee.
And finally breath. Our breath will speak to us during asana/pose. Is it fast? Slow? Restricted? While you are in an asana/pose what is your breath saying?
So the pose is made up of foundation,alignment and breath. I call this FAB! Check your foundation, notice your alignment and become aware of your breath! FAB! Then just be in the asana/pose.
Classical yoga splits the universe into two parts: spirit and matter. As humans we can work on our matter. And we can do this through asana.
"The purpose of asana is to help purify the body."- Sri K. Pattabhi Jois
There are hundreds of asana poses to choose from.
Typically a yoga class is made up of meditation, pranayama and asana (poses). A yoga teacher is a a student first and a teacher second in my opinion. Like a guide leading you through the wilderness using all the different asana available. A class, like a story, will have a beginning, a middle and an end. An asana also will have a beginning, middle and end.
"An arising, an abiding and a dissolving" - Cyndi Lee at OM yoga
The asana is like a container, your body holding you in this space and then you allow the asana to cleanse you,strengthen you, wring you, flex you, connect you.
According to Patanjali in the "yoga sutras", yoga is the stilling of the fluctuations of the mind. It is through asana that we move toward that place of more connectedness to ourselves and everyone else and this grand old universe we find ourselves in at this point in time!
A small afterthought: sitting at work at our desks can be asana! Next time you are in front of your computer, like right now: