When you breed a pokemon for battle. There are some pokemon that are stronger than others in certain stats. Jolteon is very good with Special Attacks and having a high Speed. So you would want to put EV's (Effort Values) into Jolteon's Special Attacks and Speed so that you can max those out. You decide how much EV's you want to put in a stat in a pokemon, you can only put a maximum of 510 EV's in a pokemon.
When someone asks for EV spread usually they are looking for the following: Example:
252 SP.ATK, 168 SPEED, 84 HP
You can check IV's with an IV battle (take 6 recently hatched pokemon go for a wifi battle that levels up the pokemon to 100 and enter their level 100 stats into an IV calculator) or use Action Replay to check IV's. Though sorry I am not interested in Charizard as it is not what I am looking for. Good luck with your thread.