Uncle blocks (or Ommer) are created when two or more miners create blocks at nearly the same time. Only one block can be mined and accepted as canonical on the blockchain. The others are uncle blocks, which are not included but still provide a reward to their miners for the work done.
Uncle blocks are important to Ethereum as it helps to secure the network and allows for shorter block times. Users can view uncle blocks by going to Etherscan's View Uncles page.
View Uncles Page
- Block Height: The block height where an uncle block is included.
- Uncle Number: The block height that was "uncled" and are not built on by the miners on the canonical chain.
- Age: The time when the uncle was mined.
- Miner: Miner who mined the uncle block.
- Reward: Reward given out to the miner for mining an uncled block.
Navigating an Uncle Block page
- Uncle Height: Block height where the uncle block is found.
- Uncle Position: Uncle position indicates the index of the uncle block. Maximum of 2 uncles are allowed per block.
- Block Height: The block height where the uncle block is included.
- Hash: The hash of the block header of the current block.
- Parent Hash: The hash of the block from which this block was generated, also known as its parents block.
- Mined by: Miner who mined the uncle block.
- Difficulty: The amount of work required to mine a new block.
- Gas Limit: Total gas limit provided by all transactions in the block.
- Gas Used: The total gas used in the block of gas filled in the block.
- Timestamp: The date and time the uncle block is included.
- Uncle Reward: Reward for mining the uncled block.
There are two types of rewards given to miners involving uncle blocks which are mining reward and inclusion reward. You can read more about it here.