A Z-score is a statistical measurement that describes a value's position relative to the mean of a group of values. It indicates how many standard deviations a data point is from the mean. A Z-score of 0 means the value is exactly at the mean, while a Z-score of +1 indicates the value is one standard deviation above the mean, and -1 means it is one standard deviation below. Z-scores are commonly used in various fields, including psychology, finance, and quality control, to identify outliers or to standardize scores for comparison. By converting different data sets into Z-scores, analysts can easily compare values from different distributions.