Answer:
That depends how far back they time-traveled or where. What point in history did they travel too exactly. Let's say they, or you, traveled back a handful of years back. You're currently 18, and went back when you were 10. You'd see a younger version of yourself and other people you may or may not recognize.
Step-by-step explanation:
It's all explained in the movies, the are somewhat scientifically accurate in the smallest ways. For example, changing the smallest thing the day you went alters the next 8 years of your left you've already lived.
Hope this helped! :)