Often called the King of Poses, the headstand is great for overall body circulation and energizes the nervous system. Blood returns to the upper body thereby stimulating the digestive organs as well.
Balancing on your head forces you to use a completely different set of muscles than when standing normally. It also gives you a different perspective on life in general so enjoy!
I often use this pose during the winter months to warm up the whole body. Once you get proficient at it you will want to perform it wherever you go. Try it in public for a good reaction from your friends.
You may want have a partner hold your legs to help learn the balance. Otherwise you can rest your legs against a wall, just make sure to place your head close to the wall (about 5 to 8 cm.).
Note: Pregnant women should not practice this pose.