What is exocytosis?

The movement of molecules from within the cell to outside the cell.

Think of a cell as a house. In order to get into or out of your house, you need to either enter/exit through the door. Similarly, in order for molecules to move in to and out of the cell, they need to cross the cell membrane. When molecules move into the cell, it is known as 'endocytosis'. When molecules move out of the cell, it is known as 'exocytosis'.