EVs are Effort Values. Underlying numbers that raise a pokemon's base stat, causing that stat to grow more upon leveling up (provided you don't use rare candies)
in X and Y, EVs can be manipulated in Super Training. You cannot see the exact number of EVs you have, but the hexagon shows how your EVs are spread out. Each pokemon can get up to 510 EVs, and each stat has an EV cap of 252. If you wanna split it almost 50% for Noivern, you can do 252 Special Attack (training until they tell you SpAtk is maxed) and 252 Speed (train until they tell you maxed) and then put the remaining 6 in HP. When your pokemon is "fully super trained", it has 510 EVs divided up among its stats whether you put them there through super training or if it just happened while you were playing. You picked the right generation to learn about EVs, because fully EV training in super training only takes about 2 hours at most. In older games, you had to do this tedious regimen that took at least 7 hours. "Perfect" EVs for a pokemon are considered to be putting the EVs where it counts the most. A perfect EV'd Noivern has maxed Special Attack and maxed Speed.
IVs are individual values, and are a bit more tricky. IVs are underlying values given to your pokemon upon hatching, and cannot be altered no matter what. The only way for you to manipulate IVs is by breeding, and it is very complex to do. If you're not interested in going full competitive, I would suggest not bothering with IV Breeding because it will drive you crazy. IVs can be found using an online IV calculator, although there is no working one for Generation 6 right now because it is so new. The difference between IV and EV is that you cannot change your IVs at all.