This style is not for beginners. The practice is energetic and links the asanas (poses) together with fluid movements. Ashtanga yoga was made in the 1940s and conceived as an exercise, so be ready to get your heart rate up. An Ashtanga class follows a specific sequence of poses that are always done in the same order.
You can consider Ashtanga to be a work out all on its own. It is physically demanding and has a fast pace, so it works as a great intersection between yoga flow and fitness.