Ethereum network, as well as other Ethash coins, has the uncle and orphan blocks.
An uncle is a block that is not on the longest chain. Ethereum incentivizes miners to include a list of uncles when they mine a block to decreases centralization incentive and increase the security of the chain by augmenting the amount of work on the main chain by that done in the uncles (so no work, or at least much less work, is wasted on stale blocks).
An uncle block has a significantly lower reward than a normal block. Uncle blocks are marked with a special "Uncle" tag in the blocks list.
An orphan is a rejected block. Most often it appears when another pool finds the same block solution some small amount of time (a couple of ms) faster than our pool.
An orphan block has no reward at all. These blocks are marked with a special "Reject" tag in the blocks list.