They Determine Your Pokemon's Potential in Comparison to Others of the Same Species, Indicating How Good They Can Be Once Fully Powered Up. Ivs Are Broken Down...
They determine your Pokemon's potential in comparison to others of the same species, indicating how good they can be once fully powered up. IVs are broken down into three statistics: attack, defense, and stamina (HP). Each of these statistics has an IV of 0 to 15.
It is 100% more important than CP. That is exactly why if I have a pokemon only halfway through its CP potential but being low on IV and a pokemon at 100CP but has max IV, I'd rather put all my candy on that max IV pokemon.
IV's are an important part of playing competitive Pokemon. This is all that fans need to know about the mechanic. Caring about Pokemon IVs often spells out the difference between a casual Pokemon gamer and a competitive one. A player can easily cruise through the game series without bothering with IVs.