I like to do yoga as my main exercise. Its influenced by hatha yoga.
Where does yoga originate from? 
it dates back to the pre vedic indian traditions, its also mentioned in Rigveda but i think it really got known around the 5th and 6th century BCE
Is yoga a cardiovascular exercise? 
It involves holding the stretches as a low impact type of exercise and usually used as a therapy
Is it often incorporated with other exercises? 
Not usually, yoga is usually done in a class. it involved meditation, some imagery, breath work and of course music is included.
So it is a very formal procedure.