<human>:  What is the difference between a pie chart and a bar graph?
<bot>: The main difference between a pie chart and a bar graph is that a pie chart shows parts of a whole, while a bar graph shows comparison between different categories. In a pie chart, the size of each "slice" or section of the pie indicates the quantity or proportion of each value. A bar graph has one axis with categories that are being measured and another axis that represents a quantitative value. The bars are placed side-by-side and have different heights corresponding to the values being measured.