Liferay Picklists are predefined lists of string values that consist of a name/key pair and can include any number of items. Once a list is created, you can add it to Object definitions using the Picklist field type. You can then use this field to filter displayed entires or define custom entry states. If used to define states, you can also associate custom business logic with each state using validations and actions.

Using Picklists
Managing Picklist Permissions
Picklists API Basics