There are certain fields whose values depend on another field's value. You can create dependencies between two picklist fields and define the filter values.

For example, assume we have two picklist fields - "Game category" and "Games".

Game category contains the following values
Outdoor sports
Indoor sports 

Games contains the following values
Soccer
Chess
Carrom
Rugby
Baseball
Billiards
Table Tennis

On selecting Indoor sports - the following values will be filtered
Chess 
Carrom 
Table Tennis 
Billiards

On selecting Outdoor sports - the following values will be filtered
Rugby 
Soccer 
Baseball

Important Notes:

* This function will not be supported when a record is imported or added using API's.
* The parent field can only be a picklst field.
* The child field can be either a picklist field or a multi-select picklist field.

To map field dependencies:

1. Click Module tab.
   Note: Module refer to Job Openings, Candidates, Clients and Client Contacts tab.  
2. Click Customize the [module] detail.
3. Click Map dependency field.
4. In the Map dependency fields page, click Add dependency field.
5. Select the Parent field from the drop-down list.
6. Select the Child field from the drop-down list.
7. Select the values for each parent field value. 
8. Click Save. 

Note: This feature is available only in Paid edition.