(aka Geometric objects in r ) A geom is the geometrical object that a plot uses to represent data in r. A ggplot2 geom tells the plot how you want to display your data in R. A geom defines the layout of a ggplot2 layer. People often describe plots by the type of geom that the plot uses. For example, bar charts use bar geoms, line charts use line geoms, boxplots use boxplot geoms, and so on.