Histograms visualize quantitative data or numerical data, whereas bar charts display categorical variables. Bars should touch in a histogram to illustrate that the data is along a numerical axis. The different spacing between bars is an important graphing convention and one of the most telling visual distinctions between histograms and bar charts. To summarize, both histogram vs bar graph are composed of bars, but that’s really where the overlap stops. They have varying use-cases, display different types of data, and have specific formatting rules.