The confidence level is a percentage of times you would expect to obtain the same answer or estimate, if you ran a given experiment time and time again. The area within the bell curve contains the sample size of all the experiments, but narrowing it down to, 95% accuracy for example, with be the confidence level. The confidence interval is the left and right limits of the sample size within the bell curve, depicting certainty. The closer percentage to the mean with give you a more narrow interval, while the further away from the mean will give you a much greater interval. One common use would be for a farmer or an owner of an orchard, to confidently tell their customers, that a given crop that produces fruit, has an average weight of X and assign a confidence percentage to that. This may have to be done each year due to insect damage, droughts, excessive rains... but given a number of bushels with a range of weights, a business would accurately depict the weight of their goods