I do yoga on a regular basis and it helps me alot mentally and physically. It's that 1 hour that I only focus on my poses and not think about work.
Yoga is absolutely one of them exercise. It requires a lot of physical effort, as well as mental one.
While practicing yoga, you'll improve your stamina, flexibility, and strengthen your muscles. Moreover, it's a form of mental health training. Yoga helps fight anxiety, depression and mental disorders, if any.
It depends on the level. Some yogic movements, postures, and stances require immense physical strength. They require arm strength, core strength, glute strength, and cardiovascular strength. Nonetheless, yoga is regularly performed by beginners and amateurs. It is exercise either way. Hope this helps :)