Keith E. Peterson asked:
> Is there a difference between reachability and satisfiability?

Reachability is concerned with the general problem of the existence of a path between point A and point B. (Propositional) satisfiability is concerned with determining if an assignment of values to variables exists that makes a given formula true.

You can probably connect the two by considering point A to be an empty assignment, and point B to any of the class of assignment that simplify the formula to "true". Then reachability would ask if we can augment our starting assignment to one in the class of satisfying assignments. But I'm not sure if this contributes much to a discussion on satisfiability.