Selfish mining

Theoretically, a miner publishes a new block as soon as they discover it. However, this is not enforced

Knowledge of the previous block is necessary to create the next one. The block header contains a previous block hash

The discoverer of a block can conceal it for some time to give themselves a head start. This improves their probability of discovering the next block as well

However, this can be risky. If a different version of the block is found and published first, it has a higher probability of being accepted by the network