How to Write a Smart Contract on Solana to Trade Ether

DeFi is the system of crypto exchanges and financial products that live on blockchains. If you want to swap some Ether for soul, you find a bridge. You send your Ether to the bridge's smart contract in Ethereum, which locks it up. The bridge's off-chain computer program sees this and alerts its Solana smart contract,. It gives you the equivalent of the Ether on the Solana blockchain. Bridges are notorious sites of risk in crypto.