An orphan block is a block that is created, but not accepted by the blockchain network.
The term orphan block is commonly used in cryptocurrency terminology which refers to a valid mined block that has been discarded.
Sometimes orphan blocks are also referred to as “stale blocks.”
It is created when two miners find two valid blocks approximately the same time and both submit it to the network.
An orphaned block is first accepted by some nodes, while the other block receives more proof of work. Then the orphan block is marked invalid because it is not part of the longest chain.
Nobody knows if a block is orphaned until the longest chain is determined.
Generally, miners do not receive rewards for orphan blocks.