You have 9 battle stats.

HP and MP I don't think I need to explain...

Speed determines the battle order. Who ever has the highest speed goes first and so on. If more than one person has the same speed level, then just compromise...

Spirit determines how effective curative spells are on you.

Attack is your weapon power and Strength is you character's power. Multiply them together to find how much physical damage you cause.

Magic is used to determine how much damage your magic attacks cause.

Evasion... here is where it gets tricky. You have evasion and m.evasion.
What ever you evasion is, thats the chances you have to evade physical attacks.
What ever your m.evasion is, thats the chances you have to evade magic attacks.
To see if your attack hit the target, you have to use a dice roller. Roll a 100 sided die one time and give it no bonus.
If the number you get is higher than your target's evasion, then you hit them. It's really kind of simple...

You can use the dice roller provided below. After it opens, hit the keys:

J 1 ENTER 0 ENTER

The 'total' displayed in the upper right corner is the number that you want to use.
After that, just press the key:

R

each time you need to see if your attack hit.