The member countries of PARLACEN are Guatemala, El Salvador, Honduras, Nicaragua, Dominican Republic and Panama. (Costa Rica has not joined). It is the political arm of the Central American Integration System (SICA), founded in the late 1980s to "strengthen the dialogue, the common development, democracy and pluralism as fundamental elements for peace in the region and for the integration of Central America."
From the website of the parliament:
Parlacen acts as the regional and permanent organ of political and democratic representation of the SICA with the aim of realizing the Central American integration. It seeks to achieve a peaceful coexistence within the framework of security and social welfare, not only based on a representative and participative democracy, but also in pluralism, in respect for national legislation and International Law....
The PARLACEN is composed of 20 representatives of each member state....Furthermore, former presidents and vice-presidents of the Central American states remain members of the PARLACEN, even after their term of office, for a duration laid down in the constitutions of each individual country.
Each member state elects its representatives and deputies in accordance with its national electoral law.