The document discusses determining equivalent states in a deterministic finite automaton (DFA) and using them to minimize the DFA. It provides an example of a DFA over the alphabet {a,b} recognizing strings with an even number of a's. The states {[Ea,Eb], [Ea,Ob]} and {[Oa,Eb], [Oa,Ob]} in this DFA are equivalent and can be collapsed into single states, creating a smaller minimal DFA with equivalent state partitions. The example DFA is then refined step-by-step to show the equivalent state partitions.