Bah, take two because whoops window closed by text. >_>
Description is... a very useful tool. =p It helps convey not just what something looks like, but how they act, how something happens, etc. Taking dialogue for example, description can help compliment it. E.g. '"Oh, nothing's wrong," she said.' vs '"Oh, nothing's wrong," she said quiet, biting her lip.'- while that's a pretty minor detail it helps suggest that something is wrong, or that she's annoyed.
In another example, say a Pokémon is using water gun on another Pokémon. While you can describe what the attack looks like, you can also describe how it's performed, and how the Pokémon act/react to it too. Considering the effects of a battle on each of the fighters, and also the setting (e.g. the dirt becomes muddy from all the water attacks), the trainers, etc, would add a fair bit to the battle, as it becomes more 'real' and easier for the reader to visualise everything that's happening. (But of course, describe too much and you'll just lose the reader).
Good description will also give more information than what it says. For example... 'The Pokémon cried out' would suggest it's in pain. Better yet, 'The bright glow of the Charmander's tail suddenly dampened to little more than a flicker of light' suggests that the attack really did a lot of damage to it, and without ever mentioning that fact directly/bluntly.
I suppose it's worth mentioning senses too - it's good to describe the smell of something, a sound, etc.
So I guess, really, description is a tool that you can use in a bunch of ways to add to the writing. It can make it more interesting, it can help convey additional information to the reader, and it doesn't really take much to do that either quite often. That's probably the problem with saying what it is, because it's pretty broad, haha. Hope that's at least some help? Specific examples would be cool too I suppose.
Hmm, I didn't recall posting it elsewhere, but I suppose I (or Astinus) may have. Was a while ago after all.
And heh, yay for Ludicolo sweep! I also have a video, if you have the battle recorder in your X&Y game. SY6G-WWWW-WWW5-MB2Q (gotta input that into it I think with a net connection though... so idk if you can see it).