Lizard Lady,
Yes yoga is wonderful exercise. to get the benefits of aerobic exercise, flow yoga is the closest thing to aerobics. At first one learns the postures but eventually they are done at a good pace.

Static or yin yoga is done by holding a posture for several minutes to achieve more flexibility. This is beneficial but does not give the aerobic benefits of flow yoga.

If you want to try yoga, youtube has many teachers. I find Adrienne to be very helpful and laid back. Search for Adrienne Yoga Complete Beginners and she has also many other classes on youtube.