Final answer:
In ggplot2, mapping refers to linking data variables to visual properties called aesthetics, which are crucial for the graphical representation of data.
Step-by-step explanation:
In ggplot2, the term mapping refers to the connection between variables and aesthetics. Mapping is a concept used to specify how data is linked to the visual properties of the plot – such as color, shape, size – which are known as aesthetics. Aesthetics are an essential part of the grammar of graphics, as they allow for the visual representation of data variables.
For instance, one might map the variable 'weight' to the aesthetic 'size' to visually represent heavier items with larger points.