Mainnet

Mainnet is the term used to depict when a blockchain protocol is fully developed and sent, implying that cryptocurrency transactions are being communicated, confirmed, and recorded on a distributed ledger technology (blockchain).
Rather than mainnet networks, the term testnet depicts when a blockchain protocol or network isn't yet going on its full capacity. A testnet is utilized by software engineers and designers to test and investigate every one of the viewpoints and elements of a blockchain network before they are certain the system is secure and ready for the mainnet send off.
At the end of the day, a testnet just exists as a working model for a blockchain project, while a mainnet is a completely developed blockchain platform for users to send and receive cryptocurrency transactions (or whatever other sort of digital data that is recorded on a distributed ledger).
Normally, before the mainnet of a blockchain project is sent off, the team will set up an Initial Coin Offering (ICO), a Initial Exchange Offering (IEO), or whatever other means that can assist the project with raising funds and develop their community. Ordinarily, the collected funds are then used to foster the models of the blockchain network, which is then tried during the testnet phase. Subsequent to performing bug fixes and contingent upon the performance of the testnet, the team will then, at that point, send off the mainnet form of the blockchain, which is (preferably) fully sent and functional.
In 2017, numerous blockchain startups chose to perform ICO crowdfunding occasions. To do as such, the majority of them decided to issue their own ERC-20 token on the Ethereum network. These tokens were then distributed to financial backers' wallets, as per their contribution during the ICO phase.
After the ICO crowdfunding is complete and the blockchain is fully conveyed, the team might release their mainnet, which will have their own native coin (on a proprietary blockchain) as opposed to the recently issued ERC-20 token. Right now, a cycle known as mainnet swap happens, where the ERC-20 tokens are swapped for the coins of the new blockchain. After the mainnet swap is completed, outstanding tokens are generally obliterated with the goal that main the new coins can be utilized.
Regardless of the prevalence of Ethereum and the ERC-20 standard, there are numerous other blockchain platforms that support the issuance of digital tokens (e.g., Stellar, NEM, NEO, TRON, and Waves).