A quantile is a statistical measure that divides a dataset or probability distribution into equal-sized parts, expressing the value below which a certain proportion of the data falls. For instance, the median represents the 50th percentile, indicating that 50% of the data points are below this value. Quantiles are often denoted by percentiles (such as the median, quartiles, deciles, or percentiles), where quartiles divide the data into four equal parts, deciles into ten, and percentiles into hundred parts, allowing for an understanding of the distribution and relative position of specific data points within a dataset.