exclusive disjunction/nonequivalence
Exclusive disjunction means that only one can be true, but not both. It's basically an XOR.
Affirmation/Validity/Tautology
Everything is always evaluated as true
P | Q | X ---------------- 0 | 0 | 1 0 | 1 | 1 1 | 0 | 1 1 | 1 | 1 ----------------