I would like to know the idea behind the working of 'docking' in applications. I have worked with applications where components from individual forms are docked on a single main form to provide the necessary GUI. But I don't have any idea whats happening in the background.

According to Wikipedia
A dock is a graphical user interface element that typically provides the user with a way of launching, switching between, and monitoring running programs or applications.

Now I am a bit confused if it is some component or an event or a property or something else.

EDIT : The applications was developed in Delphi on windows platform. There is something more in Delphi (manual dock and automatic dock).