Quote Originally Posted by John_Douglas View Post
Я видел, как ты выходил из дома вчера, куда ты ходил? it's like asking "where did you go yesterday" you might have left the house and come back multiple times, visited multiple locations, etc.

куда ты съездил? which is the perfective of ездил, referring to a single trip there and back.
I'm pretty sure that "куда ты ходил?" by itself can be understood as referring to a single trip there and back -- because a round-trip is, by definition, not in one direction only!

But "куда ты сходил/съездил?" serves to emphasize clearly and definitely that there was just ONE trip there and back, avoiding the ambiguity of the non-prefixed form.