Mainnet & Testnet Network
Mainnet Network is the original and functional blockchain network where the actual transactions take place in the distributed ledger and the real cryptocurrencies have real economic value in other words, mainnet refers to the actual open-source blockchain itself which is publicly verifiable.
Testnet Network is an alternative blockchain Network to be used for testing. The testnet coins are different from the real coins and do not have any value. This allows app developers or testers to experiment without having to use real Coins or worrying about breaking the main blockchain chain.