# Overview

Before beginning programming the more complicated sections of Booking.com Supply API, a provider should first be familiarized with how to retrieve the following Booking.com system information categories relevant for their project:

* [countries](/connectivity/docs/b_xml-countries) — generates a list of country names and codes used in the API
* [countrycurrencies](/connectivity/docs/b_xml-countrycurrencies) — generates a list of country codes with the currency codes the provider **must** use for each.
* [creditcards](/connectivity/docs/b_xml-creditcards) — generates a list of credit card names and their codes used in the API (both B.XML and OTA codes in use)
* [currencies](/connectivity/docs/b_xml-currencies) — generates a list of currency names and their codes used in the API