Looks like you just discovered the world of competitive battling. I'm not as knowledgeable about the subject as I used to be, but I can ahelp you with a couple of the definitions you mentioned in your post.
IV's: Individual Values. A hidden number in the game. A value of 0-31 is randomly assigned to each of a pokemon's six stats when you first catch/obtain them in the games. This attributes a sense of randomness to a pokemon's stats so that two pokemon of the same species and level can have slightly different stats.
EV's: Effort Values. another hidden number in the game. Effort values are points that are awarded to certain stats for beating in-game pokemon. A defeated pokemon awards EV's to the winning pokemon in a stat that the defeated pokemon is particularly strong in. Over time, these EV's have an adverse effect on your pokemon's stats.
Competitive battlers like to manipulate these to create the most statistically powerful pokemon for their teams. The former usually by hacking and the latter by careful training in the game (there is a limit to how many EV's one pokemon can earn)
Sweeper: simply put, a pokemon that has strong attack and speed stats at the expense of defense. In the competitive scene, these pokemon hit hard ot do massive damage.
Wall: A pokemon with high defenses used to stall or set up more intricate strategies in a competitive battle.
Tank: A pokemon with high HP and high Attack that can deal heavy damage and take several hits before going down in a competitive-level battle.
SRing: I'm not sure, but it might refer to the attack Stealth Rock and its usefulness in battle. but again, I'm not sure. >_>
I know I'm usually not that great at explaining things, so if you feel like learning more,
Smogon is the best place to get started. :P