Piggy banks are those programs that allow the withdrawal of the capital at any time, usually with the deduction of a percentage of 5-10%, sometimes but rarely without any commission.

Many programs of this type are  based on the cryptocurrency Bitcoin, in this case we call them "Piggy Bank BTC Only".

In some cases Piggy bank programs offers the Compounding. This mean  auto-reinvest your daily interest, so it is added to your principal to receive a bigger interest the next days. This option should be considered with caution