Dependent picklists are picklists (including multi-select picklists) in which the values available in the picklist depend on the value of another field, which is called the controlling field.
Controlling fields that are picklists are fields with at least one and fewer than 300 values. These are used to help with efficient, accurate data entry and help to achieve consistent data.
To define a dependent picklist, navigate to the field's area of the appropriate object.
For standard objects, this is carried out by navigating to Setup | Customize | (select the appropriate standard object) | Fields. Click on Field Dependencies.
For custom objects, navigate to Setup | Create | Objects | (select the appropriate custom object). Click on Field Dependencies.
Now click on New, choose a controlling field and dependent field, and then click on Continue.
Use the field-dependency matrix to specify the dependent...
