The testnet is a separate blockchain from the Stacks mainnet analogous to a staging environnment. It's a network used by developers to test their apps, smart contracts, or changes to the protocol in a production-like environment. It produces blocks at roughly the same rate as mainnet; about 1 block every 10 minutes on average. The Stacks testnet is rarely reset.
The hosted Stacks Blockchain API for the testnet is available at this base URL:
The testnet faucet provides you with free Stacks Token (STX) to test with. These are not the same as STX on mainnet and have no value. You can get STX from the faucet on the Stacks Explorer Sandbox, or using the API.
To get STX tokens from within the Explorer Sandbox, navigate to the "Faucet" tab and click "Request STX" button. If you would like to get enough STX tokens to try out Stacking, and click "I want to stack."
The Explorer Sandbox requires you to login with a Secret Key