Solana is fast because several engineering choices that other chains treat as separate are designed to work as one pipeline. Transactions are ordered, fetched, executed and propagated with as little waiting as possible. The headline number is throughput, but the more interesting achievement is reducing idle time.
A clock before consensus
Proof of history is best understood as a cryptographic clock. A continuously computed sequence gives validators evidence that one event came after another without asking every participant to agree on the time first. Consensus still exists; the clock simply gives it an ordered stream to work with.
Many transactions at once
Solana transactions declare the accounts they will read and write. That lets the runtime identify work that does not conflict and execute it in parallel. Two trades touching unrelated markets do not need to stand in the same line.
Propagation without one giant packet
Turbine breaks block data into smaller pieces and distributes them through a tree of validators, an approach that resembles peer-to-peer file sharing. Each participant forwards only part of the load, helping the network move large blocks quickly.
The bill still arrives
The tradeoff is demanding hardware, operational complexity and a higher cost to validate. Fast blockspace is not free; Solana chooses to pay for it with machines and network engineering so users do not pay for it in transaction fees.