A more thorough explanation:

A port of departure is a harbor where ships begin their journey by loading cargo and passengers. It is also the place where customs officials are stationed to check the cargo and people leaving the country.

For example, if a ship is leaving from New York to go to London, New York is the port of departure. The ship will load all the cargo and passengers in New York before starting its journey.

Another example is when a person is leaving the country by air. The airport they leave from is their port of departure. Customs officials will check their luggage and passport before they leave the country.

Overall, a port of departure is the starting point of a journey by sea or air, where cargo and people are checked by customs officials before leaving the country.