A Mainnet is the main network of a cryptocurrency.
When a new token or ICO appears on the market, it usually does not yet have its own blockchain. Many new tokens run as ERC-20 tokens because they run on Ethereum's network of the same name. These tokens eventually want to move to their own blockchain. When a coin transitions to its own blockchain, we call it the mainnet, the coin's main network.
Before a currency switches to its own mainnet, all functionalities are tested. The functionalities are tested on a so-called "testnet. Ethereum's testnet is Goerli. When a new coin or token is created on the Ethereum network, it is first tested on the Goerli network. Testing is done behind closed doors and, unlike the mainnet, is not open to the public. When everything works as it should, the test network is transferred to a mainnet.
When a coin switches to its own mainnet, the use of the blockchain changes. This means the coin must be modified to fit the new blockchain. This often results in a name change as well. For example, Vechain (VEN) changed to Vechain Thor (VET) after the token swap. A token swap usually happens automatically in an exchange or broker's wallet. For example, 10 VEN is then converted into 1000 VET. So tokenomics sometimes change even when switching from a testnet to a mainnet.
