What Is an ‘Orphan Block’ and How Does It Relate to Transaction Confirmation?

An orphan block is a valid block that is not part of the main, longest chain because another block was found and broadcast by a different miner almost simultaneously, winning the race. The transactions within the orphan block are not confirmed and will be returned to the mempool for inclusion in a future block.

A higher confirmation requirement helps prevent an attacker from intentionally creating a short competing chain that results in 'orphaned' deposits.