Nebulous
Legend
I know OP already got his answer, but to use one mechanic to explain another, it's like getting Advantage on the damage roll(s). Roll what you normally would -TWICE- and take the better of the two.
That's exactly what it is, Damage advantage instead of To Hit advantage.
Me, personally, I'm a fan of the houserule where if you roll a 1 or 2, it's automatically converted to a 3 (for example) so no re-rolling is required. I like to use that ability as a magic weapon perk.