Glossary
Faucet
A web service that gives away small amounts of a testnet token (or, historically, a mainnet token) to developers and new users, rate-limited per address.
Without a faucet you cannot pay gas to deploy on a testnet, and you cannot bootstrap a fresh mainnet account either. A faucet hands out small amounts on request, gated by some Sybil-resistance — a GitHub login, a small mainnet balance, a captcha, a social proof.
Bitcoin had the very first faucet in 2010: Gavin Andresen gave away 5 BTC at a time. Most modern faucets are testnet-only, since handing out free mainnet ETH at any meaningful rate would bankrupt the operator quickly.