MVC( Model View Controller) Separation of concern:
1.Model will hold the Business class information
2.View will hold only UI part (Aspx or Razor Pages)
3.Controller will hold the Business logic. Based on the user request it will call particular View along with Model Data.
4.In MVC we are maintaining the Business Logic, UI Part and Business Class are in separate places. This kind of Separations only we are calling as Separation of concern.
5.This separation of concern allow u to maintain the large application easily.