aryan migration
They came from the steppes of Central Asia. They were nomadic tribesmen who herded cattle. Through the mountain passes in the impassable Hindukush and Karakkorum mountain ranges, they migrated to the Indian subcontinent.

 

 

swift moving chariots
They traveled in swift moving light weight chariots, pulled by horse, and took by surprise the existing civilization in the subcontinent, who had so far seen only heavy logged wheels.

cattle wealth
Cattle was wealth to them.