Explain the significance of the “door of no return”

"Door of No Return" is what they called the passage the African Slaves passed through before being shipped out around the world and sold. The meaning of the name is quite clear: none of them ever retured to their home after leaving. The "Door of No Return" can be found at the House of Slaves on the Gorée Island, just 3km off the Senegal's shore. It is a museum and memorial for the Atlantic Slave Trade.