Sealevel
Plain English
The part of Solana that runs multiple programs at the same time, like a computer that can do many tasks simultaneously instead of one at a time. This is why Solana can process thousands of transactions per second - it’s not waiting in line.
Technical
Solana’s parallel smart contract runtime that enables concurrent transaction processing. Unlike sequential VMs, Sealevel processes non-conflicting transactions in parallel by analyzing which accounts each transaction will read/write. Transactions declare all accounts they’ll access upfront, allowing the runtime to schedule parallel execution across CPU cores, dramatically increasing throughput.