Parametric Equations are written with respect to time. A regular equation (Cartesian) uses only x and y values. Parametric equations come in pairs; For example, given x(t)=4t and y(t)= t^2, the goal is to eliminate "t" while combining the two equations. To do this, solve for "t" of the easier equation; x(t)=4t turns into t=x/4. Take that and substitute it into the "y" equation which gives you y=(x/4)^2 and you are done!