Answer:   In some scenario’s, we should be able to control one of the field (Dependent field) from another field (Controlling field).
For example: if we select Country (Controlling field) as US then City (Dependent Field) should display only US cities.
We can use checkbox data type fields also while creating dependent picklist (Note: Checkbox should be always controlling field)
We can use multi-select data type fields also while creating dependent picklist (Note: multi-select data type field should be always dependent field)