Error
You can make an error or two when you test hypotheses. You might say things are different when they are not. You may miss a relationship that really exists. These are called Type I and Type II errors, respectively.

Power
How about finding real differences or relationships? You want that power!
Power is an easy idea in the statistical world. You want to correctly reject a false Null Hypothesis. Power is the probability of correctly rejecting a false Null Hypothesis. It means the chance of finding what you are looking for!