Individual Values or IVs are a very important system in Pokemon Go which determines how strong your Pokemon is beyond his CP rating that you see in-game.
Each Pokemon has its own Attack, Defense and Stamina stats. The IVs can increase these stats by 0-15 additional pts. The individual values can’t be changed, as not all Pokemon are born the same. When I’m saying the same it means none of them have the same stats, size, attack and defense pts.
You have probably figured it out by now that all of your Pokemon are different by the attack, defense and stamina stats. This is what you should also remember because these are the main IVs. Also, keep in mind that IVs are not the same as base stats, because the base stats only increase when a Pokemon evolves and the IVs stay the same, ALWAYS!
IVs are very important, as it makes each Pokemon unique and determines the true power and strength. Now you know why your specific Pokemon is better than your friends, even though you’re both same Lvl and his/her Pokemon is maxed out.
The difference between IVs with 0% and 100% score is only 10% of CP and battle performance.
To determine IVs there are three options: you use a calculator and do it manually, or check out The Silph Road online calculator, or you can use the game itself. Also, if you are on an iOS system you might want to check out PokeGenie app, and for the Android users, I recommend Calcy IV app.