When you want to show how often values occur across a range for one variable, you group the data into intervals and compare how many observations fall into each interval. A histogram does exactly that: it uses adjacent bars whose heights represent the frequency in each interval, and the bars touch to reflect that the data are continuous from one interval to the next. This makes the overall distribution—its shape, spread, and any gaps or skew—easy to see at a glance. A bar graph is for categorical data, so the bars are separated to indicate distinct categories. A circle (pie) chart shows parts of a whole, not a frequency distribution across a range. A stem-and-leaf plot displays actual data values and frequencies, but it isn’t the quickest way to compare frequencies across many intervals like a histogram.