Since Lightroom is a Non Destructive editor, in other words whatever adjustments you make to an image it doesn't change the original (you can always revert, go back, to the original without any degrading of the image), I suggest you use them and find out for yourself exactly what they do.
Thanks. I tried these two sliders and they looked very similar to me. That's why I asked the question.
Distortion affects the curvature of the image (It removes or creates pincushion distortion or barrel distortion)
Vertical changes the verticality of lines in the image (makes lines more vertical or less vertical)
By the way, as a learning tool, if you drag those sliders to +100 and -100, there's no way you could miss the effect or confuse the two.