This is the 432nd most frequent Italian word.
principale
Main; principal.
Here, 'principale' describes 'porta', indicating that it is the main or most important door.
La porta principale dell'edificio è chiusa.
The main door of the building is closed.
In this sentence, 'principale' qualifies 'obiettivo', highlighting it as the primary or most significant goal.
Il mio obiettivo principale è imparare l'italiano.
My main goal is to learn Italian.
'Principale' here specifies 'organizzatore', denoting him as the chief or leading organizer.