The independent variable is the one you use or have first.
Eg. Y=x+4
Normally you have an x value then you plug it into the equation to get the y value.
So the x is the first value. It is independant. The y is the second value it depends on what x is.
This can be extended to normal and statistical meaning to.
Whether or not you are wearing wet weather gear is dependent on whether or not it is raining.
It does not work the other way around. Putting wet wrather geat on will not MAKE IT rain. So the rain is the independent variable.