A Petri net is a
finite state automaton in which transitions are
many to many: they can lead from multiple states to multiple states.
As a consequence, the states are to be regarded as individual conditions. The (global) state of a Petri net is described by the set of conditions that hold; a transition can occur iff all enabling conditions hold, and its occurrence causes all of them to no longer hold.
This models a notion of synchronization.