Hi
TKStoll2005 and welcome to Smogon!
In the future I would recommend asking in the
Simple Questions Thread (each subforum has their own, I've just linked you to ours) as it is not necessary to create a whole new thread for this.
Onto your question, all/most pokemon on Battle Spot have either been bred/caught in XY or RNG'd in BW/BW2. While some hacked Pokemon can make it through Pokebank, they usually aren't allowed on Battle Spot due to BS's better security checks, although thing's that have been 'legit hacked' (all their info corresponds to something that is legitimately available) have been known to make it onto BS iirc. One thing for sure is that you won't run into any obvious hacks like Wonder Guard Spiritomb or Sturdy Shedinja.
Any serious battler will have Pokemon with flawless IVs and will be EV trained. Of course at the lower end of the ladder you will run into people who do not have perfect Pokemon (usually in-game teams etc). Afaik you cannot
create Pokemon via Powersaves, but there are a lot of clones running around which are perfectly legal as far as we are concerned (you can even request for cloned, battle-ready Pokemon
here if you are planning on having a serious go at Battle Spot, as we understand that breeding can be a chore sometimes
Separate from Battle Spot are the battles you can have with Passersbys on the PSS, while I don't play battles there I have heard of people using hacks in those battles, so be careful...
Nintendo also runs weekend tournaments such as the
Halloween Party or the
Fairy Face-Off where it is necessary for Pokemon to have the 'Pentagon' that signifies that they are Kalos / Gen VI born, so no chance of hacks there. Also when ORAS is released, its Battle Spot will have the Pentagon rule in effect in all battles, effectively eliminating the chance of hacks from the game!
Anyway hope that answered your questions!