It’s a web site Pokémon GO Info, you can check the best moveset, weaknesses, max CP and also ranking of any Pokémon.
This video show the best moveset of Drogonite, Vaporeon and Gyarados.
Select the Pokémon you want to check. It will show the best moveset of Quick move and Main move with highest dps (damage per second). Also show the weaknesses.
Compare with the moveset of your Pokémon.