Congruent means "same" in mathematics and you have evidence to prove it. You can look at two puppies with the exact same fur color and be like "yeah they're the same". If they are the same size and shape they're congruent. This is why the AAA postulate can't work because triangles can have the same angles yet be different sizes. If figures are not congruent, they can't be similar and figures that aren't similar can't be congruent either.
