The First Quartile (Q1) is a statistical measure that represents the value below which 25% of the data points in a dataset fall. It is a way to divide a dataset into four equal parts, helping to understand the distribution of the data. Q1 is calculated by finding the median of the lower half of the dataset, excluding the overall median if the number of data points is odd. In a sorted dataset, the First Quartile is useful for identifying outliers and understanding the spread of the data. It is often used in conjunction with the Third Quartile (Q3) and the median to create a box plot, which visually represents the data's distribution and variability.