Basic contact information is stored in the contact's default properties. This includes information such as contact name, company, phone numbers, addresses, and email addresses. Additional properties are stored in extended fields.
There are 2 types of extended fields:
When you create, update, or retrieve contacts,
you'll find extended field data in the contact object under info.extendedFields
.
Most system fields are read-only, while all custom fields can be written to.