Whats the difference between motor oil formulas?

Does anybody know the difference between the formulas?





Examples 5W-30, 10W-30, 10W-40, 20W-50 ?





just a question thats been bugging me..Whats the difference between motor oil formulas?
To put it to you in layman's term is...the first number is the weight or viscosity of the oil. the second number is the additives they have added to protect the motor as if it were that weight. The higher the number is thicker the more the oil SEEMS to protect. I use an example like this...think of pancake syrup. when it is cold it is hard to pour, but when you heat it up the easier it is. Oil is the same way, when it's cold it is thicker that it is when it is hot. The hotter the oil is the thinner it is which causes your oil pressure to drop. It's not a good idea to put the thicker oil in because the added pressure will cause your bearing to wear away quicker because of the friction and heat. I hope that I explained it enough for you to understand.