The Mainchain is the original blockchain in a network. Just like a ledger in traditional finance, it is a digital record of all transactions that have occurred since its inception. In the context of Bitcoin, the Bitcoin blockchain is the Mainchain. In the world of cryptocurrencies, all the transactions made with a particular type of cryptocurrency are recorded chronologically and publicly on its Mainchain. This record-keeping helps promote transparency and traceability.
While the Mainchain handles the bulk of transactions and serves as the pillar of the blockchain network, it is sometimes coupled with smaller, separate blockchains known as 'Sidechains'. Sidechains allow certain transactions, operations, or even different cryptocurrencies to be used without overloading the mainchain. They operate independently yet are able to communicate with the Mainchain when necessary, thus improving efficiency.
The Mainchain's importance stems from its ability to provide trust, security, and transparency. It is open to anyone who wants to participate in verifications, thus keeping the process democratic. Its design ensures that a change in transaction records is next to impossible, thus giving assurance to its users about the security of their transactions. Moreover, the Mainchain's public availability ensures that anyone can trace a transaction if needed, making the process transparent.