A free trade area is a group of countries that agree to remove tariffs, quotas and similar barriers on most trade between themselves, while each member keeps its own trade policy towards the rest of the world. The deal that creates it is a free trade agreement (FTA), explained in full on that page.
Because outside tariffs differ, members use rules of origin to stop goods entering through the lowest-tariff member. A customs union goes further by adding a common external tariff. Examples include the area created by the USMCA; see also trade bloc.