Bar Graphs are a way of presenting or recording data. Along the bottom axis is the categorical data and up the left side are the numerical data. There are tall rectangles that set a numerical value to each category. Remember that there are gaps between each bar.
Histograms are another way of presenting or recording data. Along the bottom axis are the numerical ranges or values. Up the left side are more numerical values. There are no gaps between bars and each interval is the same length apart.