TL;DR
Devnet and Testnet are separate Solana networks for testing where tokens have no real value, allowing developers to build and test applications without risking real money.
Mainnet-beta is the real Solana network where tokens have value and transactions are final. Devnet is a testing network for developers to build and experiment — you can get free Devnet SOL from faucets. Testnet is used primarily for validator testing and Solana core development. All three run the same software but are completely separate: Devnet tokens have zero value and aren’t transferable to Mainnet.
New protocols typically launch on Devnet first for testing before Mainnet deployment. If a project has a working Devnet version, it shows actual development progress (vs vaporware). You can test dApp interactions on Devnet without risking real funds. Developers use Devnet to test smart contracts, and auditors verify code there before Mainnet launch.
Some projects run Devnet testnets where early users can try features and potentially qualify for airdrops. Paper trading platforms use Devnet for risk-free practice. When evaluating a new DeFi protocol, check if they have a Devnet deployment — it’s a sign of legitimate development. Be cautious of projects claiming to be “live” when they only have a Devnet presence.