If you play any third generation games (Ruby, Sapphire, Fire Red, Leaf Green, and Emerald), you should know that a Pokemon's stats aren't determined soley by their base stats and individual (now called diversification) values. In the third generation, EVs and natures are used to sort of customize a Pokemon's stats. When any Pokemon is born or caught, it has a static nature that will never change. This nature will allow your Pokemon to obtain higher stats in some areas and lower stats in other areas. For instance, if you are using a Slaking as a physical sweeper, you would most likely use the following set:
Slaking (F) @ Choice Band
Trait: Truant
EVs: 252 Atk / 252 Spd / 6 SDef
Adamant Nature (+Atk, -SAtk)
-Return
-Focus Punch
-Shadow Ball
-Earthquake
I'll get to the EVs later, but the bold text is what I want you to look at. (By the way, always post movesets in this format because it is much easier to read than the way you posted your team.) There are twenty-four different natures in the game, and each makes one stat 10% greater and another stat 10% lower, with the exception of neutral natures, which don't alter anything. The
Adamant nature raises a Pokemon's attack stat and lowers its special attack stat. Since Slaking should never be using a special attack, the nature doesn't hurt at all, but in fact only makes Slaking stronger. The problem with deciding on natures comes when you get to mixed sweepers, so I won't go there for now. Check out
this link for a comprehensive list of natures. It takes patience to breed for Natures, but once you have a good one (e.g. Adamant, Jolly, Impish, Modest, Timid, Bold, Calm, Careful, etc.), you can breed it to other Pokemon with ease thanks to Emerald's feature Everstone breeding.
Now we come to EVs or effort values. Every Pokemon gains EVs when it defeats an opposing Pokemon. There is a set number of EVs for each Pokemon that the opponent gains for defeating it, but I don't know any of them off hand since I don't play the GBA games. Use Google or ask someone else for more info on that. Anyway, each Pokemon can obtain a maximum of 510 EVs in total and no more than 255 for each stat. To find out in what way the EVs affect this Slaking, we divide each stat's EVs by four and discard the remainder. The quotient is added to Slaking's total stats. There is no point in using more than 252 EVs per stat because it is the highest number up to 255 that is divisible by four. In this case, my Slaking gains 63 stat points in attack and speed, as well as 1 extra stat point in special defense. Since the Strategy and Movesets board usually is used for competitive battling techniques, you will almost always see EVs and natures since you don't have to train Pokemon on NetBattle. I hope I've helped. Take care.