What is a suppressed exception and when do you encounter one in practice?

A suppressed exception is a secondary exception attached to a primary one rather than masking it, accessible via Throwable.getSuppressed().

The common source is try-with-resources: if the try body throws and then a resource's close() also throws, the close() exception is suppressed so the original is propagated. Knowing this matters in production debugging, because the real root cause is the primary exception and the suppressed array often shows cleanup failures that would otherwise look like the cause.