what AP RATIOS are?

That for every 100 AP he gains, 70 damage on to his Q.

Really?

Say he has 700 AP flat. And His Q does 300 + 70% AP So his Q would do 300 + 70%(490) = 790 Damage.

For low AP ratio champs you want to focus magic pen more than flat AP. For instance Zyra.

for teemo on his Q

80 / 125 / 170 / 215 / 260 (+ 80% AP)

meaning for every 100 ap you get your Q will apply 80 of it plus the base damage

so 80+80% ap of 100 ap would be 80+80ap=160 magic damage 125 +80ap= 205 magic damage , 170+80ap=250 magic damage , 260+80ap=340 magic damage

of course this is all before reduction from magic resistance

now for nunu on his ult is 625/875/1125 + 250% ap

meaning for the same 100 ap nunus ult does 625+250%ap(250) for 875 magic damage , 875+250ap=1125 magic damage , 1125+250ap= 1375magic damage

This is joke, right?

Thank you for your answers

it means for 70% of your AP is added as damage to the spell damage, before mitigation and penetration are taken into account.

for example.

If you have 100 AP, it will get 70 extra damage if you have 10 AP, it will get 7 extra damage. if you have 500 AP , it will get 350 extra damage. etc