silly spark plug question

[ryota]

Just curious... I was looking at some spark plugs and there are more than I remembered. I read on here that NGK and Denso are the ones I should go with since they are the OEM replacements, but which ones to get? is there really that much of a difference between the copper, platinum, double platinum, and iridium? BTW, I have nothing done to my engine it is completely stock, I just want to keep my engine happy and healthy since the nice weather has let me experience the outside world finally.