According to the Roadmap, Cardano launched Shelley terminating his testnet.

Shelley will be launched in phases, starting with a closed test network, which will then be extended to all users, and then will move to a hybrid phase to allow users to upgrade from Byron code. After all users are updated, mainnet will boot up and a truly decentralized staking network will be created. Hardfor blockchain Cardano will move from static association to dynamic decentralized model ...

Shelley will create a solid foundation for other Cardano eras to be launched later. At the beginning, IOHK decided to research the market and user interest by creating Incetivized Testnet (ITN). The role of ITN was to obtain data on parameters such as rate (ADA), number of rate pools created and network quality. ITN has been operating since the end of last year. ITN Staking has already received 12 billion ADA tokens, which is just over 40 percent of the total supply in circulation, and more than 1,000 staking pools have been created.

All Byron users were enrolled in the ITN run, which contained all the code and connector necessary to start the Shelley upgrade process, in particular the Ouroboros Byzantine Fault Tolerance Protocol (OBFT). Following OBFT, which is the staking protocol for the Cardano blockchain, there will be a Shelley Upgrade Phase and will end with a Shelley Hybrid Phase.

Shelley and Byron OBFT will be launched next week for major Daedalus customers and will run alongside Shelley Haskell's testnet.

Testnet Haskell will initially only be available to a select group of staking pool operators who will participate in Shelley's internal “alpha test”. Then the command line for the Shelley test node will be launched for the rest of the operators and users. The alpha test will allow the IOHK group to educate a selected group of operators who will later educate downstream users of the network. Once everyone has learned how to work on Shelley, the testnet ITN network balances will be checked. Balances will be consolidated, all Cardano libraries will be integrated and made widely available to all. Performing a balance check will lead to the final termination of ITN as a testnet.

Turning off Byron will result in a Shelley hybrid phase which will have two different blocking methods - one will be by all registered staking pools and the other by a federation of IOHK, Emurgo and Cardano Foundation.

The federation will not receive rewards for mining blocks and will subsequently withdraw them from block production. It is not certain how long the entire process will take, but once all Cardano epochs have been implemented, subsequent network upgrades will be much faster and smoother.

The new improved Cardano.org website will be launched in the coming weeks and will feature tons of documents, tutorials, guides, videos and other presentation material on Cardano.