what is the independent variable simply

The independent variable is the factor in an experiment or study that is intentionally changed or manipulated by the researcher to investigate its impact on a dependent variable. It's the variable you think might cause an effect on another variable. It is called "independent" because it should not be changed by any other variables in the experiment. For example, if you are testing the effect of sunlight on plant growth, the independent variable would be the amount of sunlight the plants receive.