What is power?
Power is the probability that we can correctly reject the Null hypothesis, or the probability that we correctly get a small p-value.
Note: if the null hypothesis is correct, then the Power does not apply.
This is what it looks like when the power is high, aka, getting the correct small p-value has high probability:
This is what it looks like when the power is low:
How to use power in application
We can increase Power by increasing the number of data points collected. Check Power analysis for more details, which would tell us how many measurements we need to correct in order to have a good amount of power.