Yoga cultivates health and wellbeing (physical, emotional, mental and social) through the regular practice of a range of many different techniques, including postures and movement, breath awareness and breathing exercises, relaxation and concentration, self-inquiry and meditation.
Yoga and Qigong are extremely complimentary to each other and often overlap in the physical exercises. They also have the same aims and use the same principles, namely moving energy through the body, using movement and breath to calm and heal, and to develop a sense of self awareness and appreciation of ourselves, others and the world around us.
They also are aligned in that yoga talks about energy moving through the nadis and storing energy, this is also true of Qigong just the names are different - qigong talks of meridians as in Chinese Medicine.