Cell interval in a histogram refers to the width of each bar in the histogram. It is calculated by dividing the range of the data by the number of bars. The range is the difference between the maximum and minimum values in the data set.
The cell interval is important because it determines the level of detail that is shown in the histogram. A smaller cell interval will result in a histogram with more bars, which will show more detail. A larger cell interval will result in a histogram with fewer bars, which will show less detail.