what part do sparks play with our cars? Why are they needed exactly? Sorry, noob question I guess, lol
Just like your noob answer said, in your combustion engine your gas is ignited by the spark allowing your engine to power your car.
As far as your second question why one is better than the other. It has to do with the "quality" of spark, and the longevity of the plug itself. Let's say you were to use a non precious metal like tin to make the spark plug. The way a spark plug is designed the spark appears in the little gap. Well if that were made from tin it's safe to say the plug would melt pretty fast in such a high heat environment, rendering your plugs and your car useless pretty quick. SO we use other, more durable metals, like: gold, iridium, palladium, platinum, and yttrium. These "more exotic" metals can withstand MUCH higher temperatures meaning you have to change them less often, and they are less prone to gunky shitty buildup. Also they can produce more powerful sparks, basically iridium can make a better spark than tin can because it can withstand more heat and more electricity. As a result, overtime the heat and current running through the spark plug errodes the curved part at the top making it larger and larger till eventually the electricity can no longer be channeled to produce a spark. One can run higher voltage to overcome this probelem, but then they just increase the errosion rate. That's why one spark plug can be better than the other.
Does that answer your question??