A Z-score is a statistical measurement that describes how far a data point is from the mean of a dataset, expressed in terms of standard deviations. A Z-score of 0 indicates that the data point is exactly at the mean, while a positive Z-score shows it is above the mean, and a negative Z-score indicates it is below the mean. Z-scores are useful for comparing different datasets or understanding the relative position of a value within a distribution. They help identify outliers and assess probabilities in the context of the normal distribution, making them valuable in fields like psychology, finance, and quality control.