Okay, so you know how when you draw a line going up and down, it looks like a wave? And when you draw another line going back and forth, it looks like a different kind of wave?
Well, a lissajous curve is kind of like if you put those two waves together in a special way.
Imagine if you had a special sheet of paper that would move up and down when one line was going up and down, and move from side to side when the other line was going back and forth.
If you drew both lines on the paper at the same time, you would start to see a really cool pattern appear - that pattern is the lissajous curve!
It looks like a squiggly shape that repeats over and over again, and it can come in all different kinds of shapes, depending on how fast or slow the lines are moving and how they're positioned.
That's basically what a lissajous curve is - two waves all mixed up and making a pretty pattern!