What is meant by the term "90% confident" when constructing a confidence interval for a mean?

90% confidence means that, if repeated samples were taken and the 90 percent confidence interval was computed for each sample, 90 percent of the intervals would contain the population mean. A 90 percent confidence interval has a 0.90 probability of containing the population mean. This means that 90 percent of the population distribution is contained in the confidence interval.