A barplot (or barchart) is one of the most common type of plot. It shows the relationship between a numerical variable and a categorical variable. For example, you can display the height of several individuals using bar chart. Barcharts are often confounded with
histograms, which is highly different. (It has only a numerical variable as input and shows its distribution). A common mistake is to use barplots to represent the average value of each group. If you have several values per group, showing only the average dissimulate a part of the
information. In this case, consider doing a boxplot or a violinplot. At least, you should show the number of observation per group and the confidence interval of each group. Last tip: ordering the bars often makes the chart more informative.