The Hedera mainnet, short for main network, is where applications are run in production with real transactions and associated costs. is the public network used to deploy decentralized applications for use in production. Transactions can be submitted to the Hedera mainnet by any application user and are timestamped and ordered automatically by the distributed ledger. Any data associated with Hedera services and stored on ledger can be accessed by any Hedera account. For each transaction, small transaction fees will be charged (in tinybars). You can find more information about transactions fees here. If you are looking to test your application or just to experiment, please check out Testnet Access, which allows you to prototype and practice in a real Hedera network without incurring those fees.