An Orphan Block is a valid block, but it is not a component of the blockchain. This type of block is produced when two miners discover a valid block (we’ll refer to these as block A and block B) at approximately the same time and transmit them both of them to the network.

Block A (the Orphan Block) is at first confirmed by some nodes (typically those geographically close to the miner) but Block B accumulates more proof of work. Therefore, Block B is confirmed by more nodes and goes on to be a parent block for the next. Block A is then labeled invalid because it isn’t a part of the longest chain. 

Note that miners do not receive a reward for Orphan Blocks.