Answer: There's no difference if you're just looking looking at the chord all by itself. But a Neapolitan chord is a major triad whose root is the lowered second degree of the key (e.g., in A minor it would be a Bb major triad). It is used as a way of approaching the V chord - most commonly when in a minor key. And it's usually in first inversion. Main thing to remember in voicing the Neapolitan chord is that its root is the upper leading tone of the tonic note and it wants to go home. So whatever voice has that lowered second degree should be the one that moves to the tonic. With typical Neapolitans it often gets there by way of a temporary detour to the leading tone, like below (tonic is A in this example):