Regarding Dual core processors

Dear Gurus,
I am curious to know the advantages of using Dual core processors
from the end user perspective.In the recent times I am hearing more
about this from Intel about their latest processor in line
products.Recently I purchased an IBM laptop which boasts about having
Intel Dual core processor.
How is it advantageous compared to normal single core processor?
When you say Dual core does that mean,it contains 2 processors(pardon
my ignorance!)?
Is dual core common in embedded world?
What support should we expect from an OS while working on Dual core
processor?(Mainly trying to understand OS level modifications needed
incase one has to move from single core to a dual core processor)