$Y$ exists when $A$ or $B$ exists but not when both $A$ and $B$ exist.

$Y$ exists only when $A$ and $B$ both exist.

$Y$ exists when both $A$ and $B$ do not exist.

$Y$ exists when $A$ exists or $B$ exists or both $A$ and $B$ exist

increases if reverse biased.

increases if forward biased.

decreases if reverse biased.

remains same in reverse and forward biasing.