Final answer:
The variable plotted on the x-axis is called the independent variable, which is the factor that can be controlled or manipulated in an experiment or data collection.
Step-by-step explanation:
When creating a graph with two axes, the variable that is plotted on the horizontal or x-axis is known as the independent variable. This is the variable that can be controlled or manipulated. Conversely, the dependent variable is the variable that responds to changes in the independent variable, and it is plotted on the vertical or y-axis. An example of this would be plotting time as the independent variable on the x-axis and distance from a station as the dependent variable on the y-axis.