Testnet, or Test Network, is a Bitcoin network used primarily for testing and development purposes. Its genesis block was created in 2011 to support software development related to Bitcoin transaction processing. Testnet allows developers to experiment without risking their actual Bitcoins, and in the process gain experience integrating Bitcoin into the applications they are working on.
Unlike the main Bitcoin network, testnet doesn’t make use of real bitcoins or mining so the developers are able to receive testnet coins for free from faucets. Testnet coins can also be obtained by mining new blocks with a testnet-compatible miner. Testnet has all the same features as Bitcoin, but none of the same value.
It is a completely independent network allowing developers to test custom rules and consensus methods, as well as introduce new features. Developers can interact with it as they would any other Blockchain, creating, executing and verifying transactions.
Compared to Regtest, this testing environment works on a global scale rather than locally. This allows developers to test code in a global network imitating the real network. Regtest only runs on local machines and is better suited to quickly test parts of the network, where global communication is not required.