Okay kiddo, so imagine you have a squiggly line on a piece of paper. Now, if you took a ruler and placed it on the line, it would touch the line at multiple points, right?
Now let's imagine you have two more lines, one that touches the squiggly line at the beginning and another at the end. The Darboux Theorem says that no matter how the squiggly line looks, you can always find these two lines that touch the squiggly line at the beginning and end without lifting the ruler.
This may sound like magic, but it's actually a mathematical fact! It's named after a French mathematician named Gaston Darboux, who figured out this theorem a long time ago. Basically, it helps mathematicians study how curves behave, even if they're super curvy and weird. Cool, huh?