Plain meaning
Start with the shortest useful explanation before going deeper.
Solana's ability to process multiple transactions simultaneously by analyzing their account access lists and executing non-conflicting transactions in parallel across CPU cores via the Sealevel runtime. Two transactions can run in parallel only if they do not share any writable accounts; transactions sharing a writable account are serialized. This design allows Solana to fully exploit modern multi-core hardware and is a primary contributor to its high throughput.