Right! The dependent variable varies depending on how something else varies (like, what's the patient's blood pressure at different dosages of a drug, or what's the person's visual reaction time at different amounts of alcohol, the speed at which a particular computer program finds information). The dependant variable is the variable who's effects you are observing. In making a graph of the data, the independent variable is placed on the X (horizontal) axis, and the dependent variable on the Y (vertical) axis.
The independent variable is that which does not depend on what's going on with something else in the experiment--the variable over which you have control and manipulate, which you vary according to your plan (like, how much of a drug you give a patient, or how many ml of alcohol someone has consumed or how much ram is in a computer).