To outperform is to accomplish something in a better or more impressive way that someone else. In a marathon, the younger runners usually outperform the very oldest ones.
Whenever you surpass or beat the record of another person, you can say you outperform them. Experienced workers frequently outperform newer employees, and pundits like to worry aloud about students in other countries who outperform American kids on standardized tests. You can also say that an investment that makes more money outperforms a less profitable one.