I've only done yoga a handful of times, do you know much about it?
I have never really done it, I have tried to meditate. I know it originated in ancient india though, and I know sort of what they do
I think it was part of my PE class in high school.  I remember very little!  What do they do?
in indian tradition, it is less physical, and more a combination of spiritual refletion, and meditative state. Of course, there is still some stretching and holding exercises 
Do you have to be in decent shape to do yoga, or can anyone do it?
I think anyone can do it, it helps a lot to reduce stress, anxiety and depression