How do the architecture in qgis plugin creation is linked with eachother using plugin builder?

I am just trying to understand how the architecture or the workflow is linked each other while QGIS Plugin creation using plugin builder. It would be better for me to understand if anyone explains with the diagram and also it would be helpful what does the following function does in the python code. I am new in QGIS Plugin creation. Help would be appreciated.

1.def init(self, iface): 2.def tr(self, message): 3.def add_action() 4.def initGui(self): 5.def unload(self): 6.def run(self):