The Golgi Apparatus is responsible for taking the proteins which were created by the ribosomes and making them bigger and better. Think of an assembly line where cars are made. The first worker creates a car frame. The next worker adds an engine, or seats, or other parts.
Ribosomes are like the first worker in the example above. They create basic proteins. The golgi apparatus then takes these proteins and adds to them, making them bigger and better.
When the golgi apparatus is done, it releases the new proteins into the cell, where they can be used to strengthen and buildup the cell.