Testnet

Testnet is the Bitcoin development environment. No one would want to use real bitcoins to test code in development. That is why the Bitcoin and testnet networks are completely separated. Bitcoin sent on testnet can be freely taken from a testnet faucet. The coins used on testnet do not hold any monetary value and cannot be converted into any currency. Other than that, they function like normal bitcoins within the confines of the test server for testing code.