If anyone's curious (like I was), a histogram has a continuous variable for it's x-axis, the bars on a histogram correspond to bins of the continuous variable. E.g. 1-10, 11-20, 21-30. In a bar graph, the x-axis is usually a discontinuous variable, typically types, with no specifically meaningful sort order, e.g. in this case, countries. Also, by convention, histograms have no spaces between bars to represent the continuity while bar graphs do to represent the discontinuity. Correct me if I'm wrong.
