In a full-wave rectifier, the two diodes are connected such that:
\begin{itemize}
\item During the positive half-cycle of the AC input, one diode is forward biased (allowing current to flow), while the other is reverse biased (blocking current).
\item During the negative half-cycle, the roles are reversed. The previously reverse-biased diode becomes forward biased and conducts current, while the other diode becomes reverse biased and blocks current.
\end{itemize}
At any given time, one diode is conducting (forward biased), and the other diode is blocking (reverse biased).