Is it correct to say that light doesn't always travel in straight lines?

Hi, I am a bit confused. I have always been taught that light travels in straight lines, which can be observed in the experiment with the 3 cards with holes in them, and when you line up the holes and shine a torch through them, you can see that the light travels in a straight line, because it passes through the holes. I know about refraction and gravitational lensing, which seem to contradict the idea that light travels in a straight line. So I was wondering if light takes a curved path, if that path can be traversed in a shorter time period, in keeping with Fermat's principle. Also I don't really understand why Snell's Law follows Fermat's Principle. Thank you for any help :)