Congruent segments are segments that have the same length.
In other words, if the length of segment DE equals the length of segment FG, then we can say the segment DE is congruent to segment FG. The symbol that we use for congruence is an equal sign with a squiggly line over it. It looks like this ⇒ ≅.
We can also use hashmarks to show that our two segments are congruent.
The image provided shows the example I was talking about above.