Custom Fields are just that, Custom fields that can be added to a person record without modifying the program. These fields can be named anything and contain the following types of data: "True/False, Date, Text Field, Year, Season, Number, Money, Phone Number, and a Custom Drop-down list. An example could be the creation of a drop-down list called "Referred By" which contains: Yellow Pages, Website, Person, etc. Another Example could be Training Class Completion Date.

This differ from properties, properties can be added to groups, persons, or family records. They are more simplistic in that they can only contain a name and a Prompt, which allows a free-form (non-typed) response. An example of this is "Disabled" with the freeform portion being "What is the nature of the disability?" Since properties are more simplistic there is no ability to create a drop-down list such as: Blind, Deaf, Wheelchair, etc.

This table (from the documentation) illustrates what types can be used for Custom Fields