Originally posted by JDMCivic
What is the difference between the first and second number?
And no I'm not a noob.:fawk: I want a simple answer. 
5w-30
5 is for when cold, like when starting the car in cold temps
30 is for the hot protection when warm, but 5w-30 has less protection than a 10w-30 in hot conditions due the additives that burn off after 1,000 miles that is needed to make a 5 weight oil.
when you go below 20 degrees you should be using a 5 or less weight.