The independent variable (x-axis) is what the scientist (or supervisor) can change themselves while the dependent variable (y-axis) is the result of the independent.
Note, just like how you graph a coordinate, you would go along the x-axis, which is the independent variable, and from there, you go up or down the y-axis because of the dependent variable.
e.g. The height of a plant DEPENDS on how much fertilizer the farmer give it.
The independent is the amount of fertilizer, because the farmer could control how much they give, and the height of the plant is the dependent variable because it depends on the independent variable.