Question

What is an independent variable?

Answer 1

It is the variable that you have control over and that doesn't have to depend on another variable. 

Answer 2

The independent variable is the variable that you change and control in your experiment. The dependent variable is the one you don't have control over and is affected by how the independent variable reacts.

For Example:
Let's say you're doing an experiment seeing how different sugars affect the density of cupcakes. The type of sugar you add would be the independent variable, because you are choosing it. The density would be the dependent variable, since it depends on the sugar used.