I found another guide that goes into much more detail for each stat, from this guide:
HP (Hit Points):
HP is a character's life. When depleted, the character will be KO'd in
battle. When the HP of all characters in your party is depleted, it
will be game over. HP is increased when a character levels up.
MP (Magic Points):
MP is used to cast Magic. Every spell requires a certain amount of MP
to be cast. The points are deducted after the casting. When you have
insufficient MP to cast a certain spell, you simply can't it.
Strength is used to power up a character's physical attacks. The
higher your Str, the higher damage you will do with physical attacks.
Vitality is used to power up a character's defense against physical
attacks. The higher your Vit, the less damage you'll receive from
enemy attacks that fall under physical attacks.
Magic is used to power up the magic that a character can use. This
includes summons as well as regular magic and enemy skills. The higher
your Mag, the higher damage you'll hit with magic.
Spirit is used to power up a character's defense against magical
attacks. The higher your Spr, the less damage you'll take from enemy
attacks that fall under magical attacks. This is an important stat,
because there is a bug in the game that causes the magical defense
that armor gives not to be taken in account. This means your magic
defense is always just your Spirit stat.
Dexterity is basically the speed of your characters, and it determines
how fast their bars will fill up. Dexterity is ALSO an important part
of a characters evasion against physical attacks. Thus, it's part of
Defense% (= Physical Evasion). The higher your Dex, the faster your
character will be, and the more physical attacks they will evade.
Luck increases the chance to perform a critical hit with physical
attacks. It ALSO increases the chance to get a 'lucky evade' in which
case you will evade physical attacks. The higher your Lck, the more
critical hits you will perform, and the more attacks you will evade.
The chance formula for getting a lucky evade is like this: % =
[Luck/4]. Max Luck (255) would give you a 63% chance because  means
you round down.