Two quantities can change together. The independent variable is the one you choose; the dependent variable is the one that follows it.

The same relationship is written three ways. The equation gives the rule, the table lists values, and the graph draws them. They all say the same thing: each unit you add to the independent variable adds the same amount to the dependent one.

Change the independent value and watch all three move together. The point on the line is the row highlighted in the table.