I have done a bit of yoga but don't know a lot about it.
Me too, a group of physical, mental, and spiritual practices or disciplines 
Do you know where it originated?
Sure! origins of yoga have been speculated to date back to pre-Vedic Indian traditions
That sound very old, what periods was that?
 sixth and fifth centuries BCE, in ancient India's ascetic and śramaṇa movements
Wow thats very old. Are there many different forms of yoga?
Yoga Sutras of Patanjali
The Yoga Sūtras of Patañjali are a collection of 196 Indian sutras (aphorisms) on the theory and practice of yoga. The "Yoga Sutras" were compiled prior to 400 CE by Patanjali who synthesized and organized knowledge about yoga from older traditions. The "Yoga Sūtras of Patañjali" was the most translated ancient Indian text in the medieval era, having been translated into about forty Indian languages and two non-Indian languages: Old Javanese and Arabic. The text fell into relative obscurity for nearly 700
Yoga
Yoga (; ; ) is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India. Yoga is one of the six orthodox schools of Hindu philosophical traditions. There is a broad variety of yoga schools, practices, and goals in Hinduism, Buddhism, and Jainism. The term "yoga" in the Western world often denotes a modern form of Hatha yoga, yoga as exercise, consisting largely of the postures called asanas.
The origins of yoga have been speculated to date back