Question

does the nature affect the pokemon if so. How?

Answer 1

A pokemon nature affects its stats, see here for an in-depth explanation: http://pokemondb.net/mechanics/natures

Answer 2

All natures excluding 5 increase 1 stat by 10% while also decreasing 1 by 10%.
They also determine a pokemons likes and dislikes poffin wise

Look here for all natures

Answer 3

Natures increase, decrease, or even out stats.

Comments

There were already two sufficient answers, read the rules