Hi Caro. For authoritative and detailed explanations, follow these two links:
ASHTANGA YOGA RESEARCH INSTITUTE
Ashtanga Yoga Background
I’m pretty new to yoga myself and I’m becoming more interested in Ashtanga so here are some basic answers to the questions you asked based on what I’ve read:[B]
What is the Ashtanga yoga exactly?[/B]
The asanas are taught in a structured, six-level method. Breath is very important.
[B]How is a lesson of Ashtanga yoga?
[/B]Either “Mysore Style” which means each person moves at his or her own individual pace or a “Led Class” where the instructor calls out the asanas everyone follows. In both types the instructor walks around the room making adjustments.[B]
Many sun’salutations with differents asanas?
[/B]There are two varieties of sun saluations and each of the six levels has different asanas.
[B]With musics or no?
[B]What is the difference with the ashtanga and the power yoga?
[/B]Power yoga is derived from Ashtanga but doesn’t follow the six levels, it’s much more free-form and marketed to let people know it’s a “workout.”