Block Chain is the most important component of any cryptocurrency network. Cryptocurrency is based on distributed, transparent public ledger where all the transactions ever made on a cryptocurrency are noted in the blocks and added to the block chain. Miners get attractive rewards to verify and create a new block and add it successfully to the Block Chain.
Here comes the twist. There will be some blocks which are created, but not accepted by the block chain network. There are called Orphan Blocks. Orphan blocks are verified and valid blocks, but not accepted by the block chain network due to a time lag in the acceptance of the block. Orphan Blocks are the rejected blocks which are very much valid. They will remain as detached blocks in the cryptocurrency network.
We know that Block Chain is a series of blocks attached to each other, with information of the previous block stored as a hash value for continuity. Miners will be constantly mining new blocks with the transactions available to earn rewards. The miner who could create a new block successfully will get the reward and the block will be added as a new unit to the Block chain.
Now a situation comes where two miners produce a similar block at the same time. This can happen because to complete the process of creating every block will take time. Acceptance of the blocks into the Block Chain won’t happen instantaneously. In the meantime, another miner may come up with the exact same block. Now there will be some confusion in the Block Chain Network, as to which of these two identical blocks should be added to the block chain.
When such tie arises, the block with the larger share of Proof of Work will be added to the Block Chain. The left over block which has comparatively smaller proof of work will be orphaned or detached. Even though it is a valid and verified block, it will not be added to the block chain and remains as an orphan block due to the delayed acceptance.
Orphan blocks are most commonly found in Bitcoin Cryptocurrency network. One more important point to note is Orphan blocks are not completely rejected. If there are any valid transactions in the Orphan block they will be added to the next valid block and thus those transactions get listed in the Block Chain.