The Simple Agreement for Vote-Escrowed Tokens, i.e. the SAVE, is a derivative which enforces that when locking DAO tokens, those tokens must be staked for a minimum duration.
SAVEs help to reduce sell pressure from grants and ensure that SAVE recipients are aligned longer-term. As they are separate tokens from the main DAO token, they do not have the same liquidity as the main DAO token and as a result are harder to dump.
For maximal composability, SAVEs are fully transferrable SPL tokens. To prevent SAVEs from being traded, one can use a lockup system such as Venko.