What does a pie chart represent?

A pie chart is specifically designed to represent the composition of a dataset, illustrating how parts make up a whole. Each slice of the pie corresponds to a category within the total, showing the proportion that each category contributes to the total value. This makes pie charts particularly effective for visualizing percentages and understanding the relative sizes of different components within a single dataset.

The other options do not correctly characterize the primary purpose of a pie chart. While relationships between two variables may be better depicted using scatter plots or line graphs, comparisons of two datasets are typically illustrated using bar or column charts. Similarly, trends over time are best visualized through line graphs or time series plots, which can effectively show changes and patterns over a specified period.