The Exclusive-OR (XOR) gate outputs true when exactly one input is true. For inputs \( A \) and \( B \), the Boolean expression is:
\[
Y = A \oplus B = \overline{A}B + A\overline{B}.
\]
This can be derived from the truth table: \( Y = 1 \) when \( A = 1, B = 0 \) or \( A = 0, B = 1 \).
Answer: \( Y = \overline{A}B + A\overline{B} \).