The Neapolitan 6th, it’s the first inversion of a b2 chord and it usually resolves to the 5 and then back to the 1, generally minor. In A minor the b2 is a Bb and here’s the first inversion. The 5 is an E chord and it’s going to resolve back to A minor.
You might contextualize it in this cycle. Watch as the bass notes move in fourths. A to D to G to C to F to B to E.
But that F to B breaks the cycle because F to B isn’t really a perfect fourth. So what if we replaced it with a Bb and there it is. The Neapolitan 6th, a cadence pretty enough to earn a name.
