Group Theory Problem

[Dragonfall]

This is from Wikipedia's "unsolved problems in math" section:

Finding a formula for the probability that two elements chosen at random generate the symmetric group Sn

Can someone explain that to me? I know what Sn is. What are these two "elements"?

[Hurkyl]

I'm not sure what's unclear. As the article said, the "elements" are random variables -- presumably independent and uniformly distributed.

If X and Y are random variables with domain Sn, then <X,Y> is a random variable whose domain is the set of all subgroups of Sn. The question is to find a formula for P(<X,Y>=Sn).