It's what makes Solana a high performance blockchain. It uses cryptography to create a synchronized clock across the network. By enabling a timestamp for every transaction, it stops validators and bots from ordering a transaction for their own benefit, a problem that other blockchains face as miners front-run transactions.
It's important to note that the history mechanism doesn't replace Solana's proof-of-stake [consensus mechanism](/learn/proof-of-work-vs-proof-of-stake/). Instead, it links together to make the proof-of-stake system more powerful. As you may know, a consensus mechanism is a process for verifying new transactions on the network and is how everyone in a decentralised crypto network can agree on who owns what crypto. Common cryptocurrency examples are Bitcoin's proof-of-work consensus mechanism and Ethereum's proof-of-stake mechanism.
While proof-of-stake makes sure validators are honest, proof-of-history makes sure they're fast. Solana uses both to produce a high-performance decentralised cryptocurrency.