The network went through three major phases: Bootstrap (3/14,2019 – 3/14,2020), Testnet (3/14,2020 – 12/28,2021) and Mainnet (12/28,2021 – the Present). During the first two phases, transfer of Pi was generally not available across the whole network. In the Mainnet phase composed of two periods—Enclosed and Open Network periods— mainnet migration and transferability became available for individual Pioneers based on the following procedures.
Unverified and unmigrated Pi in the mobile mining app is not transferable. Once you pass identity verification through the KYC (Know Your Customer) process in the Pi KYC app, and thus show that you are who you say you are (which prevents bad actors from accumulating Pi from unverified accounts), you can migrate your mobile-mined Pi balance onto the Mainnet blockchain. Once your Pi balance is migrated to Mainnet, you can send or receive your Pi to and from other Pioneers or to and from a Pi app in return for their goods or services. For how you can use your Mainnet Pi on the Pi ecosystem, see here.