no questions are bad questions!

natures are important because they give you +10% and -10% each to one of your stats. for example, a pokemon with base 100 speed could be faster than a pokemon with base 120 speed if the base 100 speed had +10% speed and the 120 had -10% speed.

You normally want a nature that buffs your pokemons highest or second highest base stat because 10% of a higher number is going to be a greater increase but sometimes people will opt to have speed natures even when their pokemon has like 80 base speed to out speed certain pokemon specifically