Definition of way ahead/way behind
In poker, a way ahead, way behind situation is, for example, a hand in which we have A2 over A-5-7. Here, with our A2, we have top pair, but with the worst sidekick. So if our opponent also has an ace, say AK, we are way behind his hand. On the other hand, if our opponent does not have an ace and has KK or QQ or JJ or another pair, we will be far ahead of his hand. In such a situation, it is not suggested to bet.
How to play the hands where you are way ahead/way behind?
Usually, when we are in a way ahead/way behind situation, we will want to check. Using our example above, if we bet with our A2, we will lose our money when we are called by better aces and we will make our opponent fold when he does not have top pair. In other words, betting when we feel we are in a way ahead/way behind situation is never a good reason. Either we lose a bigger pot or we make our opponent fold prematurely.