In the context of blockchain technology, an orphan block (or stale block) refers to a block that was successfully mined and broadcast to the network but ultimately rejected because another block with the same block height had been added to the blockchain prior to the network confirming the orphan block.
When multiple miners successfully mine a block at approximately the same time, a temporary fork in the blockchain can occur. This results in two competing blocks with the same block height. Eventually, one of these blocks is accepted by the network, while the other becomes orphaned or stale. The orphan block is disregarded, and actors who participated in its creation do not receive the associated block rewards.
Orphan blocks are a common phenomenon in decentralised blockchain networks, and they are a consequence of the distributed nature of the mining process. They do not pose a threat to the security of the blockchain; rather, they are a part of the mechanism by which the network reaches consensus on the canonical chain.
