Based on your description is sounds like the "pro" was simply explaining how pots odds relate to catching you hand. In that 1000 chip pot your opponent bets 600 chips. You must call 600 chips to win a pot that is now 1600 chips. Your pot odds
are 2.66 to 1. So in simplest terms, if the likelihood of hitting your hand and winning is better than 2.66 to 1, then you would call because you'll win enough times in that exact situation to make it profitable in the long run. Obv there is a bit more complexity that will play into it, but that's the general concept you were asking about.