instances v. threads

[Brad Tilley]

I've just started using classes in Python for some projects at work and 
have a few questions about them. I understand that once a class is 
defined that I can create many instances of it like this:

class xyz:
    def one():
       pass
    def two ():
       pass
    def three():
       pass

a = xyz()
b = xyz()
c = xyz()

a.one()
b.one()
c.one()
c.two()
c.three()

How does asynchronous/threaded programming differ from OO programming 
and classes? C is not OO and has no classes, but one can write threaded 
programs in C, right? Perhaps I'm totally off on this... can some 
explain how these concepts differ? Exactly how is an 'instance' 
different from a 'thread'?

Thanks,
Brad