Answer:   MVC Architecture – Model, View, Controller
View – It is the user interface (Apps, Tabs, Page Layouts, VF Pages, Fields and Record Types)
Controller – Business Logic (Save, Edit, New, Cancel and Delete – upon click on these button salesforce execute some logic from controller)
Model – It is the Database, which stores Schema (Meta-Data(Data about Data) –> Apps, Tabs, sObjects, fields, Apex Classes, Visualforce pages, etc…) and Instance (Records)