A single machine against a network measured in exahashes will, statistically, almost never find a block alone. Pooling converts that lottery into steady income proportional to contributed work.
Pools charge a fee, typically one to two percent, and the operator controls block construction. That concentration is a recognised centralisation concern in proof-of-work networks.
This definition is educational and not financial advice. Crypto is volatile and high-risk — always do your own research.
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