A bar chart is a visual representation of data that uses rectangular bars to show the values of different categories. Each bar's length or height corresponds to the quantity it represents, making it easy to compare different groups. Bar charts can be displayed vertically or horizontally, depending on the preference of the presenter or the nature of the data. Bar charts are commonly used in various fields, including business, education, and science, to illustrate trends, comparisons, and distributions. They are effective for presenting categorical data, such as survey results or sales figures, allowing viewers to quickly grasp the information being conveyed.