When a blockchain protocol is fully established and deployed, or when cryptocurrency transactions are broadcast, validated, and stored on a distributed ledger technology (blockchain), that situation is referred to as being on the mainnet. The phrase "testnet" refers to a blockchain protocol or network that is not yet operational to its full capacity, in contrast to mainnet networks. Before deciding whether the blockchain network is secure and prepared for the mainnet launch, programmers and developers evaluate and troubleshoot all of its components and functionalities on a testnet. In other terms, a mainnet is a fully built blockchain platform for users to send and receive cryptocurrency transactions (or any other kind of digital data that is recorded on a distributed ledger), whereas a testnet simply exists as a functional prototype for a blockchain project. A blockchain project's team will typically set up an Initial Coin Offering (ICO), an Initial Exchange Offering (IEO), or any other mechanism that can help the project raise money and expand its network before the mainnet of the project is deployed. The funds raised are typically utilized to create the blockchain network prototypes, which are then tested during the testnet phase. The team will launch the mainnet version of the blockchain once bugs have been fixed, and it will rely on how well the testnet performs and how fully deployed and operational it is (ideally). Many blockchain firms chose to hold ICO crowdfunding events in 2017. The bulk of them decided to do so by creating and issuing their own ERC-20 token on the Ethereum network. According to their investment during the ICO phase, these tokens were subsequently issued to investors' wallets. The company may release its mainnet, which will feature its own native coin (on a proprietary blockchain) instead of the previously issued ERC-20 token after the ICO crowdfunding is finished and the network is completely installed. The ERC-20 tokens are now exchanged for the currencies of the new blockchain via a procedure known as the mainnet swap. The remaining tokens are often destroyed after the mainnet swap is finished so that only the new currency can be utilized. Despite Ethereum's and the ERC-20 standard's prominence, numerous other blockchain platforms (such as Stellar, NEM, NEO, TRON, and Waves) allow for the issuance of digital tokens.