Answer:
When you calculate a statistic the result is not going to be perfectly accurate because of random errors in your observations. You therefore can give the result as one value along with a confidence interval (CI) around it.
There are two interpretations of a CI. One interpretation is that you can be confident, with the stated level of confidence, that the true value of your statistic lies within the CI.
The other interpretation is that if you repeated your experiment then, for the stated percentage of cases, the statistic would lie within the CI.