Sp can be distributed to your Stats,here's a example:
Current Players Sp:125
Atk:10
Def:10
Stm:10
Spd:10
Awr:10
Stlth:10
Player adds 30 Sp to Atk.
Current Players Sp:95
Atk:40
Def:10
Stm:10
Spd:10
Awr:10
Stlth:10
Here's a example for Ap being distributed into a Skill:
Current Players Ap:50
Lv 3 Lance Mastery:+30 to equipped Spear's weapon attack and -15 to the weight of the Spear.
Exp(Experience)Needed to Lv Up Lance Mastery:40 Ap
Player Adds 35 Ap into Lv 3 Lance Mastery.
Current Players Ap:15
Lv 3 Lance Mastery:+30 to equipped Spear's weapon attack and -15 to the weight of the Spear.
Exp Needed to Lv Up Lance Mastery:5 Ap
I hope that helped with explaining Sp and Ap's usage.