Question about stats.

I sometimes find it difficult to choose between items to wear because I dont understand how the stats work. So some questions.
1) In most rpg's strength is the ability to carry large loads and wield heavy weapons. Attack is the chances of hitting an opponent. In this game the traditional strenth does not apply, so what does it do? Also attack seems to be power generated by a blow rather the chances of a hit. Is this correct?
2) I normally think of speed as how fast a character walks and how quick he strikes a weapon, so fast speed may mean a double or even triple blow per turn. This doesn't apply in this game so what does speed do? I have Sarah equipped with the hat from that purple lizard in the marshes, which gives incredible speed but doesn't seem to give her any advantage.
3) MN or intelligence is usually used so that the higher the MN the better the spells that can be learnt. In this game the spells that can be learnt appear to be determined by level not by MN. So what does MN do?
1) In most rpg's strength is the ability to carry large loads and wield heavy weapons. Attack is the chances of hitting an opponent. In this game the traditional strenth does not apply, so what does it do? Also attack seems to be power generated by a blow rather the chances of a hit. Is this correct?
2) I normally think of speed as how fast a character walks and how quick he strikes a weapon, so fast speed may mean a double or even triple blow per turn. This doesn't apply in this game so what does speed do? I have Sarah equipped with the hat from that purple lizard in the marshes, which gives incredible speed but doesn't seem to give her any advantage.
3) MN or intelligence is usually used so that the higher the MN the better the spells that can be learnt. In this game the spells that can be learnt appear to be determined by level not by MN. So what does MN do?