Solana uses a cryptographic clock and parallel processing to be fast. Here are the most important parts of the technology.
Solana's best-known invention is proof of history. It is a cryptographic clock that proves in which order events happened.
When everyone shares the same clock, the machines in the network do not need to spend as much time agreeing on the order. That saves a lot of time.
Proof of history is not a consensus model in itself. Security comes from proof of stake, where validators lock up SOL as stake and vote on new blocks.
Solana has developed its own variant that uses the clock to reach agreement quickly.
Most blockchains process transactions one after another. Solana can process many at the same time, as long as they do not touch the same accounts.
It works like a shop with many checkouts instead of one. This is an important reason why Solana has such high capacity.
Solana also has its own solutions for spreading blocks and transactions quickly across the network. Transactions are sent straight to the validator that will produce the next block, instead of waiting in a shared queue.
The price of speed is that validators need powerful hardware. That makes it more expensive to take part, and it is one of the criticisms of Solana.