An independent variable is the variable that is changed. A dependant variable is the variable that is measured. And the control refers to all the other variables that need to be controlled in the experiment. For example, if you were to conduct an experiment to see how quickly different amounts of water boiled; the independent variable would be the amount of water, the dependant variable would be the time it took to bail and the controlled variables would be the type of water, the temperature and type of heat source, etc.
