These are the different super effective hits of the types of pokemon:
1. fight pokemon - super effective to psychc and flying hits
2. normal pokemon - super effective to fight hits only
3. rock pokemon - super effective to water, plant, fight, ground, ice and steel hits
4. ice pokemon - super effective to fight, rock and fire hits
5. steel pokemon - super effective to fight hits only
6. psychc pokemon - super effective to ghost and dark hits
7. flying pokemon - super effective to rock, ice and electrc hits
8. water pokemon - super effective to plant and elctrc hits
9. ground pokemon - super effective to water, ice, and plant hits
10. fire pokemon - super effective to water and ice hits
11. ghost pokemon - super effective to dark hits
12. electrc pokemon - super effective to ground and fight hits
13. plant pokemon - super effective to fire, ice, flying and bug hits
14. bug pokemon - super effective to fire, flying and rock hits
15. dragon pokemon - super effective to dragon hits

PS: These are very important in defeating the elite four including the champion and other trainers since this twice the result to twice the damage of the pokemon. Critical hits also twice the hit. Those pokemon with to types may have less chances in getting super effective hits or have a higher chance. Try to avoid hits that are not very effective since the hits will divide the damage to the opponent's pokemon. one-hit KO moves are very strong since it will kill the opponent instantly except if this move is missed or the pokemon's ability negates one-hit KO attacks.