The word 'parametric' is used to describe methods in math that introduce an extra, independent variable called a parameter to make them work.

For example, consider the parametric equations of a circle. The circle is defined this way using two equations. x = r cos(t)  and  y = r sin(t).

The parameter is t. It is a variable that is not really part of the circle, but any given value of is t will produce an x and y value pair that lies on the circle radius r.

The parameter is t 'drives' the equation pair to cause them to produce valid coordinate pairs.