This applies to Hive Backed Dollars (HBD) and $HIVE that are put into savings. Users do this to earn the interest paid for staking (on HBD only). At present, this is 20% as determined by consensus of the witnesses.
If someone wants to remove the HBD from the savings account. this is subject to a 3-day withdrawal period. The money that is placed in this savings account cannot be viewed as liquid. For this reason, some projects are creating derivatives of HBD on other blockchains in an effort to provide both a return along with liquidity. This is done using liquidity pools.
The 3-day withdrawal period is programmed into the base layer code.
This is a security feature available to users of Hive. If one's account does get hacked, the HBD (or $HIVE) cannot be immediately moved to another wallet. The belief is that one will notice within the 3 days and be able to reset the keys.