LiquidAccounts are EOS accounts that are stored in vRAM instead of RAM. This drastically reduces the cost of creating accounts on EOS. Another great place to understand the service is in the unit tests.
DAPP Account, LiquidAccounts implementation and code
This box contains the LiquidAccounts smart contract libraries, DSP node logic, unit tests, and everything else needed to get started integrating / testing the DAPP Network LiquidAccounts in your smart contract.