Return value vs return status of a coprocess

I don't understand this sentence about **Coprocesses** in the **bash** man page: > Since the coprocess is created as an asynchronous command, the **coproc** command always returns success. The return status of a coprocess is the exit status of 'command'. What is the difference between a "success" *return value* and a "success/error" (0/non-0) *exit status*? How differently are they handled by the **bash**? And how can one catch them to see the difference?