Wikipedia Definition: In mathematics, a Lissajous curve, also known as Lissajous figure or Bowditch curve, is the graph of a system of parametric equations.
x = A sin(at+d), y = B sin(bt)
In this graph, d is constantly changing (for the animation effect) while the other parameters can be changed to see how the graph is affected.
While searching for material on Lissajous Curve I came across this on Academo. It has a far detailed explanation on the curve than what we have here.