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?
Yeah they are Yoga Sūtras of Patañjali are 196 Indian sutras (aphorisms)