An independent variable is basically a variable that can be any number. The dependent variable is the variable calculated from the independent variable. For example, I do contract work where I get paid for every hour of work I do in a given week. If I work more hours, my paycheck is bigger. So in this case the number of hours I work is the independent variable (it can, in theory, be anywhere from 0 to 40 or more hours each week), and the dependent variable is the amount on my paycheck (it is a variable too, but it directly depends on the number of hours I worked).