A deposit for 3 years or 36 months is one of the longer maturity types of deposits and typically has a higher interest due to the length of maturity compared to a savings product or earlier mature deposit. It is offered by most major banks.
Interest from 3 year deposits can be paid monthly, semi-annually, annually or quarterly as per the following example from a large bank.
Historically the chart below shows that 3yr deposit rates remained over 10% from the late 80s to the early 90s with rates over 6% more recently in 2009-2010.