oil question

[brad`]

ok so it says to use 5w - 30w for the engine, but cant seem to find n e thing less then 10w - 30/40.

a few questions 2

differnce between synthetic and full synthetic?
5w - 30w <<---- whats it actuall mean? is it the thinkness of the oil as well as temps its ideal at?

i can see this getting outta hand with people commenting on what oil and stuff they use so would be good if someon could help sooner then later lol

cheers Brad`