Natures...

[HTA!]

What exactly do natures effect in Pokemon games?

I'm playing Fire Red (Only game I own) and have been getting quite a few with Adamant Natures.
I heard this was good....

But I'm a noob.

[Qsmash]

Natures depend on which stats get raised or lowered when Leveling up. Here's a list to help.
http://www.serebii.net/games/natures.shtml
So adamant nature is only good depending on what pokemon you have.

[HTA!]

I thought that was based on IV"s

I got an Evee, Farfetch'd, and Pidgy...
Not sure if that's good or bad...

[FruitFlow]

Natures play a major role when EV training your pokemon.
They help raise extra points in a specific stat, while lowering another.
HP is the only stat that is unaffected by this. That's where IVs come in.

Depending on the nature you have, you will gain an added 10% upward in that stat and a 10% downward in another stat.

Balanced natures, however, don't give you an increase or decrease in a stat.
They simply keep you in a neutral position, due to the fact that you gain and lose 10% in the exact same stat.
Balanced natures aren't really the best choice to choose from, unless you want to raise a certain pokemon with balanced stats of course. Also, a pokemon with a balanced nature will eat any held berry and poffin that you make.

Here's a list of the Balanced natures. There's a total of 5 of them:

Bashful (+Attack  -Attack)
Docile   (+Defense  -Defense)
Hardy   (+Sp. Attack  -Sp. Attack)
Quirky  (+Sp. Defense  -Sp. Defense)
Serious (+Speed  -Speed)


Here's a list of the other natures that give and take off stat points. There's a total of 20.
Also, just in case you're interested, I've listed they're favorite battle berries:

Lonely (+Attack -Defense)
Brave (+Attack -Speed)
Adamant (+Attack -Sp. Attack)
Naughty (+Attack -Sp. Defense)
FAVORITE BERRY: FIGY BERRY

Bold (+Defense  -Attack)
Relaxed (+Defense  -Speed)
Impish (+Defense  -Sp. Attack)
Lax (+Defense  -Sp. Defense)
FAVORITE BERRY: IAPAPA BERRY

Timid (+Speed  -Attack)
Hasty (+Speed  -Defense)
Jolly (+Speed  -Sp. Attack)
Naive (+Speed  -Sp. Defense)
FAVORITE BERRY: MAGO BERRY

Modest (+Sp. Attack  -Attack)
Mild (+Sp. Attack  -Defense)
Quiet (+Sp. Attack  -Speed)
Rash (+Sp. Attack  -Sp. Defense)
FAVORITE BERRY: WIKI BERRY

Calm (+Sp. Defense  -Attack)
Gentle (+Sp. Defense  -Defense)
Sassy (+Sp. Defense  -Speed)
Careful (+Sp. Defense  -Sp. Attack)
FAVORITE BERRY: AGUAV BERRY

Remember these well.
They will greatly improved your pokemon of the desired stat.

[JrDude]

Is ignoring natures bad? 'cause I do.

[FruitFlow]

Only if you're EV training.

[Macawmoses]

Is ignoring natures bad? 'cause I do.

It can be in a battle. If you and I both start off with a Roserade, primed for sleep powder, chances are my timid little friend will get the jump on you.

[ThePowerOfOne]

I always get Adamant in FireRed too... Oh well, good for me, I prefer attack over special attack ^__^