Call custom field values with liquid code. This provides a way for you to pull information that you've collected and saved in Custom Fields for the people in your account.
The following Liquid code template is how to call the Value of Custom Field:
{{ subscriber.custom_field_identifier }}
The subscriber keyword denotes the value from a given Custom Field Identifier.
Using the Custom fields for the profile example above, the following Liquid code returns the value of the field Identifier called shirt_size.
{{ subscriber.shirt_size }}
As the shirt size Identifier contains a value of "medium", the Liquid returns medium.