Quantiles calculated from a sample are often used to estimate their equivalent population quantiles - as where a the median of a sample (or 'sample median') is used to estimate the median of the 'population' of values that sample (hopefully) represents.

What is the purpose of quantiles?

A quantile defines a particular part of a data set, i.e. a quantile determines how many values in a distribution are above or below a certain limit. Special quantiles are the quartile (quarter), the quintile (fifth) and percentiles (hundredth).

What is the use of quantiles in statistics?

In statistics and probability, quantiles are cut points dividing the range of a probability distribution into continuous intervals with equal probabilities, or dividing the observations in a sample in the same way.